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  <title><![CDATA[TsaiKoga Blog]]></title>
  <link href="https://TsaiKoga.github.com/atom.xml" rel="self"/>
  <link href="https://TsaiKoga.github.com/"/>
  <updated>2020-03-15T23:06:52+08:00</updated>
  <id>https://TsaiKoga.github.com/</id>
  <author>
    <name><![CDATA[TsaiKoga]]></name>
    
  </author>
  <generator uri="http://octopress.org/">Octopress</generator>

  
  <entry>
    <title type="html"><![CDATA[浏览历史数据库表设计与缓存设计]]></title>
    <link href="https://TsaiKoga.github.com/blog/2020/03/15/liu-lan-li-shi-shu-ju-ku-biao-she-ji-yu-huan-cun-she-ji/"/>
    <updated>2020-03-15T14:55:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2020/03/15/liu-lan-li-shi-shu-ju-ku-biao-she-ji-yu-huan-cun-she-ji</id>
    <content type="html"><![CDATA[<h3>目录</h3>

<h4><a href="#1">1. 功能需求</a></h4>

<h4><a href="#2">2. 实现方案</a></h4>

<h4><a href="#3">3. 数据库设计</a></h4>

<h5><a href="#3.1">3.1 预测数据量</a></h5>

<h5><a href="#3.2">3.2 按用户区间分表</a></h5>

<h5><a href="#3.3">3.3 定时任务数据归档</a></h5>

<h4><a href="#4">4. 缓存设计</a></h4>

<h5><a href="#4.1">4.1 怎么存</a></h5>

<h5><a href="#4.2">4.2 哪里存</a></h5>

<h5><a href="#4.3">4.3 缓存时间设置</a></h5>

<h1 id='1'>1 功能需求 </h1>


<p>最近，公司 app 需要增加一个新的功能是历史浏览记录的页面。</p>

<p>说道 “浏览历史”，大家应该都不陌生，跟浏览器的浏览历史功能基本一致。浏览历史的功能，仅限于用户浏览文章页面，
记录用户浏览过的文章，一方面方便用户下次再次查找，另一方面，也对我们将来对用户画像设计有所帮助。</p>

<p><img src="https://TsaiKoga.github.com/images/posts/2020-03-15/history.png" title="历史记录" alt="历史记录图片" /></p>

<br/>




<h1 id='2'>2 实现方案</h1>


<p>为了记录用户浏览过的文章，我们只需要在用户访问文章详情的页面进行记录即可。</p>

<p>可以采用“异步方式”，将用户浏览过的文章记录。</p>

<p>但是目前用户上百万，每个用户一天浏览量不很清楚，但是随时间递增，这个记录一定很大；所以我们采用新建一个 RDS 实例，
专门用来存放历史记录。</p>

<p>面对庞大的数据量我们应该如何进行分表呢？</p>

<br/>




<h1 id='3'>3 数据库分表</h1>


<p>分表前，我们先思考影响这个表的有哪些变量？</p>

<p>一般都离不开 “时间” 和 “用户数”。
所以我们到底是要采用按“时间分表”还是“用户分表”呢？</p>

<br/>




<h2 id='3.1'>3.1 预测数据量</h2>


<p>我们可以到服务器上看文章详情请求数。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>cat 20200214.log | grep -E <span class="s2">&quot;articles/[0-9]+&quot;</span> | wc -l
</span></code></pre></td></tr></table></div></figure>


<p>将一天文件中的文章详情数统计出来，也可以通过脚本获取一个月的文件进行统计。</p>

<p>然后我们可以根据我们的分表方式来对数据进行预测：</p>

<p>1) <strong>通过时间-按月分表</strong></p>

<p>这时候我们需要统计一个月的请求数，大致推测一个月数据 600w 左右的浏览量。</p>

<p>2) <strong>通过用户-按用户id分表</strong></p>

<p>这个时候统计的时候要考虑 user_id 的值，通过脚本给了个平均预测，一个用户一个月 50*30 = 1500。
（较大较理想情况，因为我们就是要防止一些大用户的操作）</p>

<br/>


<p>根据数据和预测情况，我们可以简单看出其中的<strong>优缺点</strong>：</p>

<p>1) <strong>按月分表</strong></p>

<p><strong>优点</strong>：各个表数据量分布均匀</p>

<p><strong>缺点</strong>：</p>

<ol>
<li><p>由于需求要展示最近三个月的数据，那么读取数据的时候比较麻烦，需要将多个月表的数据 <code>union</code>
后，进行排序和分页，<code>union</code> 后的数据不走索引，况且分页效率有点低。</p></li>
<li><p>如果用户突然增长，月表数据可能突破限制。这时候只能再通过月表再次分表。</p></li>
</ol>


<p>2)<strong>按用户分表</strong></p>

<p><strong>优点</strong>：因为查询只针对个别用户可以充分利用索引，查询将十分简单高效，用户之间独立。</p>

<p><strong>缺点</strong>：</p>

<ol>
<li><p>由于每个用户属性不一样，阅读数不等，造成数据量不平均。</p></li>
<li><p>用户数量级庞大，分表数量庞大</p></li>
</ol>


<p>我们可以通过这两个优缺点进行取长补短，查询问题必须选用 “按用户分表”，那么如何解决用户表数量过多问题？</p>

<p>一般会有 <strong>按用户id取模分表</strong>，但是这种分表有缺点：</p>

<ol>
<li><p>数量再次增大，想要再进行扩展分表比较困难；</p></li>
<li><p>取模运算如果是通过 mysql，取模将无法走索引；</p></li>
</ol>


<br/>




<h2 id='3.2'>3.2 按用户区间分表</h2>


<p>所以我们可以选择 <strong>按用户区间分表</strong>，它呢补了上面取模的缺点，对后期单表中数据增大可以很方便继续再分；
例如我们 1w 个用户一张表，如果将来数据上亿，可以考虑变成 5k 个用户一张表，也就是在原来的基础上分成两张表，
通过脚本即可创建并迁移数据；</p>

<p>那么我们可以通过前面获得的访问量来确定大概要多少用户为一个区间；那么剩下一个问题了，当时间不短推移，
数据量还是很大，难道我们还要对再对用户分表吗？</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='php'><span class='line'><span class="nv">$suffix</span> <span class="o">=</span> <span class="nb">strval</span><span class="p">(</span><span class="nx">floor</span><span class="p">(</span><span class="nv">$user_id</span> <span class="o">/</span> <span class="nx">History</span><span class="o">::</span><span class="na">SPLIT_NUM</span><span class="p">));</span>
</span><span class='line'><span class="nv">$tablename</span> <span class="o">=</span> <span class="s1">&#39;history&#39;</span><span class="o">.</span><span class="nv">$suffix</span><span class="p">;</span>
</span><span class='line'><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">setTable</span><span class="p">(</span><span class="nv">$tablename</span><span class="p">);</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h2 id='3.3'>3.3 定时任务数据归档</h2>


<p>不，因为只展示用户最近三个月数据，所以我们可以通过定时任务<strong>对旧数据进行归档处理</strong>。
这样我们的表就一直控制在那个数据级；唯一可能上升的情况就是平均用户浏览数增多，不过影响不大，前面已经说了，
再次对用户进行划分也很简单。</p>

<p>注意，由于数据一直在这张表，所以主键就不要再用自增 id 了，因为日积月累的数据可能撑爆最大整型。可以用 <strong>UUID</strong> 或其他字符串类型等；</p>

<br/>


<hr />

<p>就此存储方案就好了，剩下显示方案；</p>

<p>关于显示，我们可以在表增加查询需要的所以，直接从中获取到我们的数据，速度很快；但是还有一个问题，就是
文章查询问题。</p>

<p>由于每篇文章可能根据运营人员更改而变动，所以一开始我们保存在浏览历史表中的数据将是关联id，例如此处是文章id；</p>

<p>这时候一种方法就是通过 <code>join</code> 文章表进行显示，但是这样三个月浏览记录去 JOIN 文章，可想而知这是一个噩梦；</p>

<p>那么我们还有另一个办法，通过缓存减少对文章的查询，也舍弃 join 文章的方法。</p>

<br/>




<h1 id="4">4 缓存设计</h1>




<h2 id="4.1">4.1 怎么存</h2>


<p>如何设计缓存呢？和分表一样，我们也需要考虑几个变量。</p>

<p>这里我们要显示的是用户某一天查询的文章的分页，所以变量将是：</p>

<ul>
<li>用户id</li>
<li>日期</li>
<li>分页页码</li>
<li>每页数量</li>
</ul>


<p>如果用结果缓存，这个组合将非常巨大，并且 redis 存储不适合一次性存储超过 150kb 的数据；</p>

<p>所以我们可以通过 <strong>片段缓存</strong> 的方式来存储；</p>

<p>1）<strong>优点</strong>：多处地方都可以使用该片段缓存，缓存利用率高；</p>

<p>2）<strong>缺点</strong>：还是需要消耗一点点性能；</p>

<p>每个文章进行缓存，这样从性能上说，每次只是在浏览历史数据库将数据分页排序后取出，</p>

<p>对一页中的数据进行循环，每次循环直接内存中读取缓存即可。</p>

<p>最坏情况，循环每页数量去数据库搜索每篇文章（这个问题可以通过缓存存储触发位置来优化）。</p>

<br/>




<h2 id="4.2">4.2 哪里存</h2>


<p>通过从产品上分析，用户是大多都是从文章列表点击文章详情进入，所以，我们可以在文章详情处就设置这个
片段缓存；当然，浏览历史的地方也要，只是浏览历史处命中率就变得非常高了，几乎已经先在文章详情处
进行了存储，所以循环取文章就变得非常少了；</p>

<br/>




<h2 id='4.3'>4.3 缓存时间设置</h2>


<p>TODO</p>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[Laravel 的数据库事务源码分析]]></title>
    <link href="https://TsaiKoga.github.com/blog/2019/05/09/laravel-de-shu-ju-ku-shi-wu-yuan-ma-fen-xi/"/>
    <updated>2019-05-09T17:54:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2019/05/09/laravel-de-shu-ju-ku-shi-wu-yuan-ma-fen-xi</id>
    <content type="html"><![CDATA[<p>在批发档口记账 app 中，由于用户数量越来越多，有几个老客户了反馈单据丢失的问题；</p>

<p><strong>打个比方：</strong></p>

<p>我们开单会去创建开单表 <code>order_create</code>，开单表会生成详情 <code>order_create_goods_sku</code>，然后生成欠货表 <code>order_owe_goods_sku</code>；</p>

<p>然后接着是发货请求，会生成发货主表 <code>order_delivery</code> 和 发货详情 <code>order_delivery_goods_sku</code>；发货会生成库存变动记录；</p>

<br>


<p>这时候已经有了开单和开单详情，证明已经开单请求成功；</p>

<p>但是库存变动记录有，发货单却找不到；这时候我去查找了日志，发现也有发货请求；
然而通过库存变动记录找不到相应的发货单了，这是怎么回事，难道是被人撤销了吗？</p>

<br>


<p>全局查找了整个项目，没有强删除的接口，难道是代码有问题？</p>

<p>那么我开始定位代码，因为事务包裹着整个&#8221;发货的创建流程&#8221; 和 &ldquo;库存变动记录的生成&#8221;；
所以要么就全部回滚，那么不太可能是回滚问题？</p>

<br>


<h1>跟踪数据库操作：</h1>

<hr />

<p>那是不是有人从数据库删除了？</p>

<p>我写了个触发器，只要有人强删记录就会记录到一张跟踪表：</p>

<p>1.首先创建跟踪表：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">CREATE</span> <span class="k">TABLE</span> <span class="o">`</span><span class="n">juniu_track_delivery</span><span class="o">`</span> <span class="p">(</span>
</span><span class='line'>  <span class="o">`</span><span class="n">track_delivery_id</span><span class="o">`</span> <span class="nb">int</span><span class="p">(</span><span class="mi">11</span><span class="p">)</span> <span class="k">NOT</span> <span class="k">NULL</span> <span class="n">AUTO_INCREMENT</span> <span class="k">COMMENT</span> <span class="s1">&#39;订单ID&#39;</span><span class="p">,</span>
</span><span class='line'>  <span class="o">`</span><span class="n">order_delivery_id</span><span class="o">`</span> <span class="nb">int</span><span class="p">(</span><span class="mi">11</span><span class="p">)</span> <span class="k">NOT</span> <span class="k">NULL</span> <span class="k">DEFAULT</span> <span class="mi">0</span> <span class="k">COMMENT</span>  <span class="s1">&#39;发货单ID&#39;</span><span class="p">,</span>
</span><span class='line'>  <span class="o">`</span><span class="n">order_id</span><span class="o">`</span> <span class="nb">int</span><span class="p">(</span><span class="mi">11</span><span class="p">)</span> <span class="k">NOT</span> <span class="k">NULL</span> <span class="k">DEFAULT</span> <span class="mi">0</span> <span class="k">COMMENT</span> <span class="s1">&#39;订单ID&#39;</span><span class="p">,</span>
</span><span class='line'>  <span class="o">`</span><span class="n">deliver_timestamp</span><span class="o">`</span> <span class="k">timestamp</span> <span class="k">NOT</span> <span class="k">NULL</span> <span class="k">DEFAULT</span> <span class="k">CURRENT_TIMESTAMP</span> <span class="k">COMMENT</span> <span class="s1">&#39;发货时间&#39;</span><span class="p">,</span>
</span><span class='line'>  <span class="o">`</span><span class="n">deleted_at</span><span class="o">`</span> <span class="k">timestamp</span> <span class="k">NOT</span> <span class="k">NULL</span> <span class="k">DEFAULT</span> <span class="k">CURRENT_TIMESTAMP</span> <span class="k">COMMENT</span> <span class="s1">&#39;被删除时间&#39;</span><span class="p">,</span>
</span><span class='line'>  <span class="o">`</span><span class="n">deleted_by</span><span class="o">`</span> <span class="nb">varchar</span><span class="p">(</span><span class="mi">50</span><span class="p">)</span> <span class="k">DEFAULT</span> <span class="s1">&#39;&#39;</span> <span class="k">COMMENT</span> <span class="s1">&#39;删除的用户ip&#39;</span><span class="p">,</span>
</span><span class='line'>  <span class="k">PRIMARY</span> <span class="k">KEY</span> <span class="p">(</span><span class="o">`</span><span class="n">track_delivery_id</span><span class="o">`</span><span class="p">)</span>
</span><span class='line'>  <span class="p">)</span> <span class="n">ENGINE</span><span class="o">=</span><span class="n">InnoDB</span> <span class="n">AUTO_INCREMENT</span><span class="o">=</span><span class="mi">0</span> <span class="k">DEFAULT</span> <span class="n">CHARSET</span><span class="o">=</span><span class="n">utf8</span><span class="p">;</span>
</span></code></pre></td></tr></table></div></figure>


<br>


<p>2.建立触发器 <code>track_delete_delivery</code> 跟踪：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">DELIMITER</span> <span class="o">//</span>
</span><span class='line'><span class="k">CREATE</span> <span class="k">TRIGGER</span> <span class="n">track_delete_delivery</span>
</span><span class='line'><span class="k">AFTER</span> <span class="k">DELETE</span>
</span><span class='line'>   <span class="k">ON</span> <span class="n">juniu_order_delivery</span> <span class="k">FOR</span> <span class="k">EACH</span> <span class="k">ROW</span>
</span><span class='line'><span class="k">BEGIN</span>
</span><span class='line'>   <span class="k">DECLARE</span> <span class="n">vUser</span> <span class="nb">varchar</span><span class="p">(</span><span class="mi">50</span><span class="p">);</span>
</span><span class='line'>   <span class="c1">-- Find username of person performing the DELETE into table</span>
</span><span class='line'>   <span class="k">SELECT</span> <span class="k">USER</span><span class="p">()</span> <span class="k">INTO</span> <span class="n">vUser</span><span class="p">;</span>
</span><span class='line'>   <span class="c1">-- Insert record into audit table</span>
</span><span class='line'>   <span class="k">INSERT</span> <span class="k">INTO</span> <span class="n">juniu_track_delivery</span>
</span><span class='line'>   <span class="p">(</span> <span class="n">order_delivery_id</span><span class="p">,</span>
</span><span class='line'>     <span class="n">order_id</span><span class="p">,</span>
</span><span class='line'>     <span class="n">deliver_timestamp</span><span class="p">,</span>
</span><span class='line'>     <span class="n">deleted_at</span><span class="p">,</span>
</span><span class='line'>     <span class="n">deleted_by</span><span class="p">)</span>
</span><span class='line'>   <span class="k">VALUES</span>
</span><span class='line'>   <span class="p">(</span> <span class="k">OLD</span><span class="p">.</span><span class="n">order_delivery_id</span><span class="p">,</span>
</span><span class='line'>     <span class="k">OLD</span><span class="p">.</span><span class="n">order_id</span><span class="p">,</span>
</span><span class='line'>     <span class="k">OLD</span><span class="p">.</span><span class="n">deliver_timestamp</span><span class="p">,</span>
</span><span class='line'>     <span class="n">SYSDATE</span><span class="p">(),</span>
</span><span class='line'>     <span class="n">vUser</span> <span class="p">);</span>
</span><span class='line'><span class="k">END</span><span class="p">;</span> <span class="o">//</span>
</span><span class='line'><span class="k">DELIMITER</span> <span class="p">;</span>
</span></code></pre></td></tr></table></div></figure>


<p>观察一段时间，仍有数据丢失，但是并没有跟踪到，初步判断不是人为删除；</p>

<br>


<h1>Mysql 事务特性：</h1>

<hr />

<p>Mysql 事务具有四大特性：A（原子性）C（一致性）I（隔离性）D（持久性）；</p>

<p>事务有五个级别：</p>

<blockquote><ol>
<li><p>TRANSACTION_NONE  不使用事务。</p></li>
<li><p>TRANSACTION_READ_UNCOMMITTED  未提交读，允许脏读。</p></li>
<li><p>TRANSACTION_READ_COMMITTED  提交读，防止脏读，最常用的隔离级别,并且是大多数数据库的默认隔离级别</p></li>
<li><p>TRANSACTION_REPEATABLE_READ  重复读，可以防止脏读和不可重复读，</p></li>
<li><p>TRANSACTION_SERIALIZABLE  序列化，可以防止脏读，不可重复读取和幻读，（事务串行化）会降低数据库的效率</p></li>
</ol>
</blockquote>

<p>1、<strong>脏读：</strong> 事务A读取了事务B更新的数据，然后B回滚操作，那么A读取到的数据是脏数据</p>

<p>2、<strong>不可重复读：</strong> 事务 A 多次读取同一数据，事务 B 在事务A多次读取的过程中，对数据作了更新并提交，导致事务A多次读取同一数据时，结果不一致。</p>

<p>3、<strong>幻读：</strong> 事务 A 修改了表中所有数据，但是事务 B 插入了一条数据，当事务 A 查询数据发现还有一条记录没有改过来，就好像发生了幻觉一样，这就叫幻读。</p>

<p><strong>小结：</strong> 不可重复读的和幻读很容易混淆，不可重复读侧重于修改，幻读侧重于新增或删除。解决不可重复读的问题只需锁住满足条件的行，解决幻读需要锁表</p>

<br>


<p>最后我们来查看一下 Mysql 数据库事务配置，看是不是事务配置错误：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
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</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">select</span> <span class="o">@@</span><span class="n">tx_isolation</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'><span class="k">select</span> <span class="o">@@</span><span class="k">session</span><span class="p">.</span><span class="n">tx_isolation</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'><span class="k">select</span> <span class="o">@@</span><span class="k">global</span><span class="p">.</span><span class="n">tx_isolation</span><span class="p">;</span>
</span></code></pre></td></tr></table></div></figure>


<p>显示结果都是 <code>READ-COMMITTED</code></p>

<br>


<h1>查看事务源码：</h1>

<hr />

<p>重新回到回滚代码，既然都被包裹起来，但是又回滚不成功，我开始查阅 Laravel API，因为我怕会是框架有问题，</p>

<p>找到相应的 laravel 版本 5.1: <a href="https://laravel.com/api/5.1/">https://laravel.com/api/5.1/</a></p>

<p>寻找 <code>transaction</code>，显示有</p>

<blockquote><p>Illuminate\Database\ConnectionInterface::transaction</p>

<p>Illuminate\Database\Connection::transaction</p></blockquote>

<p>接口定义的是规则，所以我看数据库的连接类 <code>Illuminate\Database\Connection::transaction</code></p>

<p>这里有几个我们要看的方法：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
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<span class='line-number'>7</span>
</pre></td><td class='code'><pre><code class='php'><span class='line'><span class="nx">mixed</span> <span class="nx">transaction</span><span class="p">(</span><span class="nx">Closure</span> <span class="nv">$callback</span><span class="p">)</span>
</span><span class='line'>
</span><span class='line'><span class="nx">void</span> <span class="nx">beginTransaction</span><span class="p">()</span>
</span><span class='line'>
</span><span class='line'><span class="nx">void</span> <span class="nx">commit</span><span class="p">()</span>
</span><span class='line'>
</span><span class='line'><span class="nx">void</span> <span class="nx">rollBack</span><span class="p">()</span>
</span></code></pre></td></tr></table></div></figure>


<p>点击右边行号，可以跳转到 5.1 源代码文件：</p>

<p>先查看 <code>transaction</code> 方法，此处参数是一个闭包，我们项目中使用的不是这种写法：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
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<span class='line-number'>7</span>
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<span class='line-number'>15</span>
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<span class='line-number'>18</span>
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<span class='line-number'>22</span>
</pre></td><td class='code'><pre><code class='php'><span class='line'><span class="k">public</span> <span class="k">function</span> <span class="nf">transaction</span><span class="p">(</span><span class="nx">Closure</span> <span class="nv">$callback</span><span class="p">)</span>
</span><span class='line'><span class="p">{</span>
</span><span class='line'>    <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">beginTransaction</span><span class="p">();</span>
</span><span class='line'>    <span class="c1">// We&#39;ll simply execute the given callback within a try / catch block</span>
</span><span class='line'>    <span class="c1">// and if we catch any exception we can rollback the transaction</span>
</span><span class='line'>    <span class="c1">// so that none of the changes are persisted to the database.</span>
</span><span class='line'>    <span class="k">try</span> <span class="p">{</span>
</span><span class='line'>        <span class="nv">$result</span> <span class="o">=</span> <span class="nv">$callback</span><span class="p">(</span><span class="nv">$this</span><span class="p">);</span>
</span><span class='line'>        <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">commit</span><span class="p">();</span>
</span><span class='line'>    <span class="p">}</span>
</span><span class='line'>    <span class="c1">// If we catch an exception, we will roll back so nothing gets messed</span>
</span><span class='line'>    <span class="c1">// up in the database. Then we&#39;ll re-throw the exception so it can</span>
</span><span class='line'>    <span class="c1">// be handled how the developer sees fit for their applications.</span>
</span><span class='line'>    <span class="k">catch</span> <span class="p">(</span><span class="nx">Exception</span> <span class="nv">$e</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>        <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">rollBack</span><span class="p">();</span>
</span><span class='line'>        <span class="k">throw</span> <span class="nv">$e</span><span class="p">;</span>
</span><span class='line'>    <span class="p">}</span> <span class="k">catch</span> <span class="p">(</span><span class="nx">Throwable</span> <span class="nv">$e</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>        <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">rollBack</span><span class="p">();</span>
</span><span class='line'>        <span class="k">throw</span> <span class="nv">$e</span><span class="p">;</span>
</span><span class='line'>    <span class="p">}</span>
</span><span class='line'>    <span class="k">return</span> <span class="nv">$result</span><span class="p">;</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>整个事务用 <code>try catch</code> 包裹住，如果失败，直接抛出异常，并且回滚，<code>transactions</code> 自然减为 0；</p>

<p>然后我看看我们项目中所使用的方法，通过<code>DB::beginTransaction();</code>
开始，然后中途出错，直接写 <code>DB::rollback()</code> ，
然后 <code>return</code> 返回，最后成功提交 <code>DB::commit()</code>。</p>

<p>先看看 <code>beginTransaction()</code> 的源码:</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
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<span class='line-number'>14</span>
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<span class='line-number'>16</span>
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<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
</pre></td><td class='code'><pre><code class='php'><span class='line'><span class="k">public</span> <span class="k">function</span> <span class="nf">beginTransaction</span><span class="p">()</span>
</span><span class='line'><span class="p">{</span>
</span><span class='line'>    <span class="k">if</span> <span class="p">(</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">transactions</span> <span class="o">==</span> <span class="mi">0</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>        <span class="k">try</span> <span class="p">{</span>
</span><span class='line'>            <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">pdo</span><span class="o">-&gt;</span><span class="na">beginTransaction</span><span class="p">();</span>
</span><span class='line'>        <span class="p">}</span> <span class="k">catch</span> <span class="p">(</span><span class="nx">Exception</span> <span class="nv">$e</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>            <span class="k">if</span> <span class="p">(</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">causedByLostConnection</span><span class="p">(</span><span class="nv">$e</span><span class="p">))</span> <span class="p">{</span>
</span><span class='line'>                <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">reconnect</span><span class="p">();</span>
</span><span class='line'>                <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">pdo</span><span class="o">-&gt;</span><span class="na">beginTransaction</span><span class="p">();</span>
</span><span class='line'>            <span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
</span><span class='line'>                <span class="k">throw</span> <span class="nv">$e</span><span class="p">;</span>
</span><span class='line'>            <span class="p">}</span>
</span><span class='line'>        <span class="p">}</span>
</span><span class='line'>    <span class="p">}</span> <span class="k">elseif</span> <span class="p">(</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">transactions</span> <span class="o">&gt;=</span> <span class="mi">1</span> <span class="o">&amp;&amp;</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">queryGrammar</span><span class="o">-&gt;</span><span class="na">supportsSavepoints</span><span class="p">())</span> <span class="p">{</span>
</span><span class='line'>        <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">pdo</span><span class="o">-&gt;</span><span class="na">exec</span><span class="p">(</span>
</span><span class='line'>            <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">queryGrammar</span><span class="o">-&gt;</span><span class="na">compileSavepoint</span><span class="p">(</span><span class="s1">&#39;trans&#39;</span><span class="o">.</span><span class="p">(</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">transactions</span> <span class="o">+</span> <span class="mi">1</span><span class="p">))</span>
</span><span class='line'>        <span class="p">);</span>
</span><span class='line'>    <span class="p">}</span>
</span><span class='line'>    <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">transactions</span><span class="o">++</span><span class="p">;</span>
</span><span class='line'>    <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">fireConnectionEvent</span><span class="p">(</span><span class="s1">&#39;beganTransaction&#39;</span><span class="p">);</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>可以看到，这里的 <code>transactions</code> 属性记录多少层事务，通过 <code>try catch</code> 包裹一个事务开始，如果失败，重新尝试连接，并将<code>transaction + 1</code>；</p>

<br>


<p>再看 <code>rollback()</code></p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
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<span class='line-number'>4</span>
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<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
</pre></td><td class='code'><pre><code class='php'><span class='line'><span class="k">public</span> <span class="k">function</span> <span class="nf">rollBack</span><span class="p">()</span>
</span><span class='line'><span class="p">{</span>
</span><span class='line'>    <span class="k">if</span> <span class="p">(</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">transactions</span> <span class="o">==</span> <span class="mi">1</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>        <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">pdo</span><span class="o">-&gt;</span><span class="na">rollBack</span><span class="p">();</span>
</span><span class='line'>    <span class="p">}</span> <span class="k">elseif</span> <span class="p">(</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">transactions</span> <span class="o">&gt;</span> <span class="mi">1</span> <span class="o">&amp;&amp;</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">queryGrammar</span><span class="o">-&gt;</span><span class="na">supportsSavepoints</span><span class="p">())</span> <span class="p">{</span>
</span><span class='line'>        <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">pdo</span><span class="o">-&gt;</span><span class="na">exec</span><span class="p">(</span>
</span><span class='line'>            <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">queryGrammar</span><span class="o">-&gt;</span><span class="na">compileSavepointRollBack</span><span class="p">(</span><span class="s1">&#39;trans&#39;</span><span class="o">.</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">transactions</span><span class="p">)</span>
</span><span class='line'>        <span class="p">);</span>
</span><span class='line'>    <span class="p">}</span>
</span><span class='line'>    <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">transactions</span> <span class="o">=</span> <span class="nx">max</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">transactions</span> <span class="o">-</span> <span class="mi">1</span><span class="p">);</span>
</span><span class='line'>    <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">fireConnectionEvent</span><span class="p">(</span><span class="s1">&#39;rollingBack&#39;</span><span class="p">);</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>这里 <strong>只有在 transactions 为 1 的时候，才去 rollback 整个事务</strong>；</p>

<br>


<p>再来看看 <code>commit()</code></p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
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<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
</pre></td><td class='code'><pre><code class='php'><span class='line'><span class="k">public</span> <span class="k">function</span> <span class="nf">commit</span><span class="p">()</span>
</span><span class='line'><span class="p">{</span>
</span><span class='line'>    <span class="k">if</span> <span class="p">(</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">transactions</span> <span class="o">==</span> <span class="mi">1</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>        <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">pdo</span><span class="o">-&gt;</span><span class="na">commit</span><span class="p">();</span>
</span><span class='line'>    <span class="p">}</span>
</span><span class='line'>    <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">transactions</span><span class="o">--</span><span class="p">;</span>
</span><span class='line'>    <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">fireConnectionEvent</span><span class="p">(</span><span class="s1">&#39;committed&#39;</span><span class="p">);</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>也是只有当 <code>transactions == 1</code> 的时候才会 <code>commit</code> 整个事务；</p>

<p>不像 <code>transaction</code> 闭包那样，有整个 <code>try catch</code> 包裹，这里每一个步骤都要自己控制，</p>

<p>项目中事务的写法经常是：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
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</pre></td><td class='code'><pre><code class='php'><span class='line'><span class="nx">DB</span><span class="o">::</span><span class="na">beginTransaction</span><span class="p">();</span>
</span><span class='line'>
</span><span class='line'><span class="nv">$res</span> <span class="o">=</span> <span class="nx">OrderDelivery</span><span class="o">::</span><span class="na">insert</span><span class="p">([</span><span class="o">...</span><span class="p">]);</span>
</span><span class='line'><span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="nv">$res</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>    <span class="nx">DB</span><span class="o">::</span><span class="na">rollback</span><span class="p">();</span>
</span><span class='line'>    <span class="k">return</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">fail</span><span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="s1">&#39;创建失败&#39;</span><span class="p">);</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'><span class="nv">$delivery_skus</span> <span class="o">=</span> <span class="nb">json_decode</span><span class="p">(</span><span class="nv">$color_size_matrix</span><span class="p">,</span> <span class="k">true</span><span class="p">);</span>
</span><span class='line'><span class="nx">OrderDeliveryGoodsSku</span><span class="o">::</span><span class="na">insert</span><span class="p">(</span><span class="nv">$delivery_skus</span><span class="p">);</span>
</span><span class='line'><span class="o">...</span>
</span><span class='line'><span class="o">...</span>
</span><span class='line'><span class="nx">DB</span><span class="o">::</span><span class="na">commit</span><span class="p">();</span>
</span></code></pre></td></tr></table></div></figure>


<p>那么就有问题了，如果某个步骤出错，但是因为没有抛出异常，因为查看 API 像 <code>insert</code> 失败会返回 <code>false</code>；</p>

<p>需要人工判断返回值去 <code>rollback</code>，如果没有判断，也没有 <code>rollback</code>，这样 <code>transactions</code> 就没有减到 1；
这就有可能跑到 <code>commit</code> 那里去给 <code>transactions - 1</code> 了；</p>

<h1>结论：</h1>

<hr />

<p>所以较好的方法还是，</p>

<ol>
<li><code>transaction</code> 带闭包参数；</li>
<li><code>beginTransaction + try catch</code></li>
</ol>


<p>用 <code>beginTransaction + try catch</code>，只要有问题，直接到 <code>catch</code> 那做一次回滚即可，不用担心哪里忘了 <code>rollback</code>；</p>

<p>示例：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
</pre></td><td class='code'><pre><code class='php'><span class='line'><span class="nx">DB</span><span class="o">::</span><span class="na">beginTrasaction</span><span class="p">();</span>
</span><span class='line'><span class="k">try</span> <span class="p">{</span>
</span><span class='line'>    <span class="nx">OrderModificationGoodsSku</span><span class="o">::</span><span class="na">insertGetId</span><span class="p">();</span>
</span><span class='line'>    <span class="nx">OrderOweGoodsSku</span><span class="o">::</span><span class="na">where</span><span class="p">()</span><span class="o">-&gt;</span><span class="na">update</span><span class="p">();</span>
</span><span class='line'>    <span class="nx">DB</span><span class="o">::</span><span class="na">commit</span><span class="p">();</span>
</span><span class='line'><span class="p">}</span> <span class="k">catch</span> <span class="p">(</span><span class="nx">\Throwable</span> <span class="nv">$e</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'><span class="err">   </span> <span class="c1">// For php 7</span>
</span><span class='line'>    <span class="nx">DB</span><span class="o">::</span><span class="na">rollback</span><span class="p">();</span>
</span><span class='line'>    <span class="c1">//throw $e;</span>
</span><span class='line'>    <span class="nx">Log</span><span class="o">::</span><span class="na">error</span><span class="p">(</span><span class="nv">$e</span><span class="o">-&gt;</span><span class="na">getMessage</span><span class="p">());</span>
</span><span class='line'>    <span class="k">return</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">fail</span><span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="s2">&quot;创建失败&quot;</span><span class="p">);</span>
</span><span class='line'><span class="p">}</span> <span class="k">catch</span><span class="p">(</span><span class="nx">\Exception</span> <span class="nv">$e</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>    <span class="c1">// For php5</span>
</span><span class='line'>    <span class="nx">DB</span><span class="o">::</span><span class="na">rollback</span><span class="p">();</span>
</span><span class='line'>    <span class="c1">//throw $e;</span>
</span><span class='line'>    <span class="nx">Log</span><span class="o">::</span><span class="na">error</span><span class="p">(</span><span class="nv">$e</span><span class="o">-&gt;</span><span class="na">getMessage</span><span class="p">());</span>
</span><span class='line'>    <span class="k">return</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">fail</span><span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="s2">&quot;创建失败&quot;</span><span class="p">);</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>

]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[宕机后的架构思考]]></title>
    <link href="https://TsaiKoga.github.com/blog/2019/04/18/dang-ji-hou-de-jia-gou-si-kao/"/>
    <updated>2019-04-18T10:24:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2019/04/18/dang-ji-hou-de-jia-gou-si-kao</id>
    <content type="html"><![CDATA[<h1>背景</h1>

<p>上个月公司服务器频繁宕机，第一次是因为日志撑爆了服务器，已经在[服务器日志空间解决方案-外挂磁盘]中解决了；</p>

<p>后面又有两次宕机，都是数据库 RDS 使用率太高导致的；</p>

<p>由于阿里云监控 RDS 报警不及时，所以比较难及时进行处理；</p>

<p>后来我使用了 processlist 查看：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">select</span> <span class="n">id</span><span class="p">,</span> <span class="n">db</span><span class="p">,</span> <span class="k">user</span><span class="p">,</span> <span class="k">host</span><span class="p">,</span> <span class="n">command</span><span class="p">,</span> <span class="n">time</span><span class="p">,</span> <span class="k">state</span><span class="p">,</span> <span class="n">info</span>
</span><span class='line'><span class="k">from</span> <span class="n">information_schema</span><span class="p">.</span><span class="n">processlist</span>
</span><span class='line'><span class="k">where</span> <span class="n">command</span> <span class="o">!=</span> <span class="s1">&#39;Sleep&#39;</span>
</span><span class='line'><span class="k">order</span> <span class="k">by</span> <span class="n">time</span> <span class="k">desc</span>
</span></code></pre></td></tr></table></div></figure>


<p>可以实时的观测到是哪些 sql 现在执行慢，当然这些 sql 可能本身不慢，而是因为被慢 sql 阻塞了，导致执行时间太久；</p>

<p>我们可以通过 kill 命令将进程号杀掉（需要用有权限的账号登录）；</p>

<p>这些慢 sql 是 java 的新项目部署上去没有增加有效索引导致的，而新项目 和 已经稳定并且拥有大部分用户的 PHP 项目放在同一个 ECS，数据库也是同一台 RDS；
一个库占用了大部分 CPU 牵连另一个库执行 sql，造成部分 PHP 项目的用户开始投诉；</p>

<p>不过该问题已经得到解决，目前已经为不同项目拆分不同 ECS 和 不同的 RDS；</p>

<br>


<p>当前的 PHP 项目一些表的数据也都到达 2，3k万，现在 java 的项目有数据仓，有中台；
数据增长速度会比 PHP 项目快；</p>

<p>虽然已经稳定运行，但是这件事让我思考一个问题，如果以后用户级上去了，该怎么办？</p>

<br>


<h1>每秒请求数 qps</h1>

<p>前阵子看过一篇关于架构设计的文章，这里借用他的方法来设计为当前项目的架构做分析；</p>

<p>架构设计一般通过估量 qps，然后来设计架构；</p>

<p>首先我去查看项目的 qps，因为目前项目已经在线上，可以通过动态截取每秒日志请求数来估算 QPS：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>tail -f laravel-2019-04-01.log | cut -d <span class="s1">&#39; &#39;</span> f2 | uniq -c
</span></code></pre></td></tr></table></div></figure>


<p>得出结论，大概 qps 为 100 左右；</p>

<p>目前 100 个请求每秒对于 8 核的 ECS 已经足够；</p>

<p>如果按照每个请求一秒要处理 3 个 sql 请求，那么对于 RDS 就是 300 请求每秒，也是足够的；</p>

<p>所以，就目前位置，服务器 ECS 和 数据库 RDS 都能够承载当前用户量访问。</p>

<br>


<br>


<h1>集群化部署</h1>

<h2>系统集群化部署</h2>

<p>那么以后销售人员推广力度变大，qps 将逐渐变大，那么一台 ECS 可能承载不了；</p>

<p>这时候我们可以加多一台 ECS 来拆分 qps；</p>

<p>假设 qps 为 500，我们使用“负载均衡”策略，将 qps 平分到两台 ECS 服务器上：</p>

<br>


<h3>架构</h3>

<pre><code>          |
        500/s
          |
          ↓
   { nginx 负载均衡 }
      |        |
   250/s     250/s
      |        |
      ↓        ↓
  { ECS1 }  { ECS2 }
      |        |
    750/s     750/s
      |        |
      +————————+
         |  |
         ↓  ↓
     { 数据库 RDS }
</code></pre>

<h3>简单实现：</h3>

<p>Nginx 通过 upstream 来给两台 ECS 分配权重，
以下是 tomcat + nginx 配置，PHP + nginx 也类似，只是换一下 tomcat_server 和 端口 即可</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="c"># 负载均衡到 2 台 ECS 上，一个 130 的权重为 1/3，129 的权重为 2/3;</span>
</span><span class='line'>upstream tomcat_server <span class="o">{</span>
</span><span class='line'>  server 192.168.200.130:8080 <span class="nv">weight</span><span class="o">=</span>10
</span><span class='line'>  server 192.168.200.129:8080 <span class="nv">weight</span><span class="o">=</span>20
</span><span class='line'><span class="o">}</span>
</span><span class='line'>
</span><span class='line'><span class="c"># 监听 80 端口，并转发到 tomcat_server 这个 upstream</span>
</span><span class='line'>server <span class="o">{</span>
</span><span class='line'>  listen 80
</span><span class='line'>  location / <span class="o">{</span>
</span><span class='line'>    proxy_pass http://tomcat_server;
</span><span class='line'>    root html;
</span><span class='line'>    index index.html, index.htm;
</span><span class='line'>  <span class="o">}</span>
</span><span class='line'><span class="o">}</span>
</span></code></pre></td></tr></table></div></figure>




<br>


<br>


<h2>数据库分库分表 + 读写分离</h2>

<p>但是现在有一个问题，就是数据量庞大，例如开单表已经到达了 26,934,626 条，虽然都有效的利用了索引，但是明显开单已经变慢；</p>

<p>再加上每天店铺小妹都在同一个高峰时段不停开单，若有卡顿，则可能会拖累其他 sql 执行，并且造成 CPU 使用率上升，从而宕机；</p>

<p>所以面临的问题主要是两个：</p>

<p>1：数据量太大，导致查询缓慢：</p>

<p>2：面对较大的 qps，例如前面 500 qps 已经分成两个请求 750/s 到 RDS 上；</p>

<p>当 qps 不断增加，ECS 都可以用负载均衡增加机器解决，但是系统层面上解决了，数据库层面上并发量到达 3000/s 就有问题了；</p>

<br>


<h3>解决方案：</h3>

<ol>
<li><p>通过将经常查询并且数据量大的表进行 “水平分割”；</p></li>
<li><p>分库分表 + 读写分离；
也就是把一个库拆分为多个库，部署在多个数据库服务上，这是作为主库承载写入请求的；然后每个主库都挂载至少一个从库，由从库来承载读请求。
此时假设对数据库层面的读写并发是 3000/s，其中写并发占到了 1000/s，读并发占到了 2000/s。
那么一旦分库分表之后，采用两台数据库服务器上部署主库来支撑写请求，每台服务器承载的写并发就是 500/s。每台主库挂载一个服务器部署从库，那么 2 个从库每个从库支撑的读并发就是 1000/s。</p></li>
</ol>


<br>


<h3>架构</h3>

<pre><code>                   |
              高峰 1000/s
                   ↓
           {  nginx 负载均衡  }
            |       |       |
          300/s   300/s   300/s
            ↓       ↓       ↓
   +———→ { ECS1 } { ECS2 } { ECS3 } ←————+
   |        |                 |          |
   |     500/s             500/s         |
 1000/s     ↓                 ↓       1000/s
   |    { 主库1 }          { 主库2 }       |
   |        ↓                 ↓           |
   +———— { 从库1 }         { 从库2 } ——————+
</code></pre>

<h3>简单实现</h3>

<h4>主从数据库：</h4>

<p>如果数据库是 ECS 自己创建的，需要通过开启 my.cnf 的 Binary log 功能实现 ；</p>

<p>如果是直接购买 RDS，可以购买两台，一台做主库，一台做从库，通过阿里云自带服务 DTS 同步数据；</p>

<h4>分库分表：</h4>

<p>最好的做法，是服务在 <strong>搭建之初</strong> 就设计为分库分表的存储模式，从根本上杜绝中后期的风险。
不过，会牺牲一些便利性，例如列表式的查询，同时，也增加了维护的复杂度。</p>

<p><strong>如何分表：</strong>
像 Laravel，我们可以事先写一个 model，对应这个 model 的所有分表，然后为这个 model 添加一个方法；</p>

<p>这个方法 通过传入查询条件，对每个表进行查询，然后 union 起来返回；</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
<span class='line-number'>30</span>
<span class='line-number'>31</span>
<span class='line-number'>32</span>
<span class='line-number'>33</span>
<span class='line-number'>34</span>
</pre></td><td class='code'><pre><code class='php'><span class='line'><span class="cm">/* 传入查询的开始日期和结束日期用于计算跨越的表和达到约束表数据的目的。</span>
</span><span class='line'><span class="cm">   外部可以调整查询的列，还可以添加where条件</span>
</span><span class='line'><span class="cm">*/</span>
</span><span class='line'><span class="k">public</span> <span class="k">function</span> <span class="nf">setUnionAllTable</span><span class="p">(</span><span class="nv">$startTime</span> <span class="o">=</span> <span class="nx">LARAVEL_START</span><span class="p">,</span> <span class="nv">$endTime</span> <span class="o">=</span> <span class="nx">LARAVEL_START</span><span class="p">,</span> <span class="nv">$attributes</span> <span class="o">=</span> <span class="p">[</span><span class="s1">&#39;*&#39;</span><span class="p">],</span> <span class="nv">$wheres</span> <span class="o">=</span> <span class="p">[])</span>
</span><span class='line'><span class="p">{</span>
</span><span class='line'>    <span class="c1">//约束条件</span>
</span><span class='line'>    <span class="nv">$whereConditions</span> <span class="o">=</span> <span class="p">[];</span>
</span><span class='line'>    <span class="nv">$wheres</span> <span class="o">=</span> <span class="nb">array_merge</span><span class="p">([[</span><span class="s1">&#39;time&#39;</span><span class="p">,</span> <span class="s1">&#39;&gt;=&#39;</span><span class="p">,</span> <span class="nv">$startTime</span><span class="p">],</span> <span class="p">[</span><span class="s1">&#39;time&#39;</span><span class="p">,</span> <span class="s1">&#39;&lt;&#39;</span><span class="p">,</span> <span class="nv">$endTime</span><span class="p">]],</span> <span class="nv">$wheres</span><span class="p">);</span>
</span><span class='line'>    <span class="c1">//时间戳转日期</span>
</span><span class='line'>    <span class="nv">$startDate</span> <span class="o">=</span> <span class="nb">date</span><span class="p">(</span><span class="s1">&#39;Y-m&#39;</span><span class="p">,</span> <span class="nv">$startTime</span><span class="p">);</span>
</span><span class='line'>    <span class="nv">$endDate</span> <span class="o">=</span> <span class="nb">date</span><span class="p">(</span><span class="s1">&#39;Y-m&#39;</span><span class="p">,</span> <span class="nv">$endTime</span><span class="p">);</span>
</span><span class='line'>    <span class="c1">//涉及的表数组</span>
</span><span class='line'>    <span class="nv">$tables</span> <span class="o">=</span> <span class="p">[];</span>
</span><span class='line'>    <span class="c1">//循环where数组，格式是[[&#39;字段&#39;,&#39;表达式&#39;,&#39;值&#39;,&#39; and|or &#39;],[&#39;字段&#39;,&#39;表达式&#39;,&#39;值&#39;,&#39; and|or &#39;]]</span>
</span><span class='line'>    <span class="c1">//例子[[&#39;beauty_uid&#39;, &#39;=&#39;, &#39;2011654&#39;, &#39;and&#39;]]</span>
</span><span class='line'>    <span class="k">foreach</span> <span class="p">(</span><span class="nv">$wheres</span> <span class="k">as</span> <span class="nv">$val</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>        <span class="c1">//组装每个where条件</span>
</span><span class='line'>        <span class="nv">$val</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="o">=</span> <span class="nv">$val</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="o">?</span> <span class="nv">$val</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="o">:</span> <span class="s2">&quot;&#39;&#39;&quot;</span><span class="p">;</span>
</span><span class='line'>        <span class="k">if</span> <span class="p">(</span><span class="nb">isset</span><span class="p">(</span><span class="nv">$val</span><span class="p">[</span><span class="mi">3</span><span class="p">]))</span> <span class="p">{</span>
</span><span class='line'>            <span class="nv">$whereConditions</span><span class="p">[]</span> <span class="o">=</span> <span class="s2">&quot; </span><span class="si">{</span><span class="nv">$val</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span><span class="si">}</span><span class="s2"> </span><span class="si">{</span><span class="nv">$val</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="si">}</span><span class="s2"> </span><span class="si">{</span><span class="nv">$val</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="si">}</span><span class="s2"> </span><span class="si">{</span><span class="nv">$val</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">;</span>
</span><span class='line'>        <span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
</span><span class='line'>            <span class="nv">$whereConditions</span><span class="p">[]</span> <span class="o">=</span> <span class="s2">&quot; and </span><span class="si">{</span><span class="nv">$val</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="si">}</span><span class="s2"> </span><span class="si">{</span><span class="nv">$val</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="si">}</span><span class="s2"> </span><span class="si">{</span><span class="nv">$val</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">;</span>
</span><span class='line'>        <span class="p">}</span>
</span><span class='line'>    <span class="p">}</span>
</span><span class='line'>    <span class="c1">//循环开始日期和结束日期计算跨越的表</span>
</span><span class='line'>    <span class="k">for</span> <span class="p">(</span><span class="nv">$i</span> <span class="o">=</span> <span class="nv">$startDate</span><span class="p">;</span> <span class="nv">$i</span> <span class="o">&lt;=</span> <span class="nv">$endDate</span><span class="p">;</span> <span class="nv">$i</span> <span class="o">=</span> <span class="nb">date</span><span class="p">(</span><span class="s1">&#39;Y-m&#39;</span><span class="p">,</span> <span class="nb">strtotime</span><span class="p">(</span><span class="nv">$i</span> <span class="o">.</span> <span class="s1">&#39;+1month&#39;</span><span class="p">)))</span> <span class="p">{</span>
</span><span class='line'>        <span class="nv">$tables</span><span class="p">[]</span> <span class="o">=</span> <span class="s1">&#39;select &#39;</span> <span class="o">.</span> <span class="nb">implode</span><span class="p">(</span><span class="s1">&#39;,&#39;</span><span class="p">,</span> <span class="nv">$attributes</span><span class="p">)</span> <span class="o">.</span> <span class="s1">&#39; from cdb_honey_log_&#39;</span> <span class="o">.</span> <span class="nb">date</span><span class="p">(</span><span class="s1">&#39;Yn&#39;</span><span class="p">,</span> <span class="nb">strtotime</span><span class="p">(</span><span class="nv">$i</span><span class="p">))</span> <span class="o">.</span> <span class="s1">&#39; where 1&#39;</span> <span class="o">.</span> <span class="nb">implode</span><span class="p">(</span><span class="s1">&#39;&#39;</span><span class="p">,</span> <span class="nv">$whereConditions</span><span class="p">);</span>
</span><span class='line'>    <span class="p">}</span>
</span><span class='line'>    <span class="c1">//会得到每一个表的子查询，因为都有约束条件，所以每一个子查询得结果集都不会很多</span>
</span><span class='line'>    <span class="c1">//用setTable的方法把这个子查询union all 后 as一个表名作为model的table属性</span>
</span><span class='line'>    <span class="c1">//sql大概会是:(select xxx,xxx from honey_log_20177 where time &gt;= 开始日期 and time &lt; 结束日期 and xxx union all select xxx,xxx from honey_log_20178 where time &gt;= 开始日期 and time &lt; 结束日期 and xxx) as cdb_honey_log</span>
</span><span class='line'>    <span class="c1">//核心是看你输入的开始日期和结束日期和约束条件，组装成一个union all的子查询然后作为table赋予model</span>
</span><span class='line'>    <span class="k">return</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">setTable</span><span class="p">(</span><span class="nx">DB</span><span class="o">::</span><span class="na">raw</span><span class="p">(</span><span class="s1">&#39;(&#39;</span> <span class="o">.</span> <span class="nb">implode</span><span class="p">(</span><span class="s1">&#39; union all &#39;</span><span class="p">,</span> <span class="nv">$tables</span><span class="p">)</span> <span class="o">.</span> <span class="s1">&#39;) as cdb_honey_log&#39;</span><span class="p">));</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>不过，最好还是使用 <strong>数据库中间件</strong>，数据量再大的时候，放到 Elasticsearch 里面，自带分片处理，交给他底层实现。</p>

<br>


<br>


<h2>缓存</h2>

<p>当 qps 再次上升，系统层面可以加机器，但是数据库其实本身不是用来承载高并发请求的，</p>

<p>所以通常来说，<strong>数据库单机每秒承载的并发就在几千的数量级</strong>，而且数据库使用的机器都是比较高配置，比较昂贵的机器，成本很高。；</p>

<p>或者原先没有分库分表，想分库加机器又觉得贵；</p>

<p>对于这两个问题，可以通过引入缓存解决；</p>

<p>根据 <strong>“二八定律”</strong>，80%的请求只关注在20%的热点数据上。因此，我们应该建立 服务器 和 数据库 之间的缓存机制。</p>

<p>这种机制，可以用磁盘作为缓存，也可以用内存缓存的方式。通过它们，将大部分的 <strong>热点数据查询</strong>，阻挡在数据库之前;</p>

<p>可以根据系统的业务特性，对那种写少读多的请求，引入缓存集群。</p>

<p>写数据库的时候同时写一份数据到缓存集群里，然后用缓存集群来承载大部分的读请求，这里可以使用 Memcached 或是 Redis 实现；</p>

<p>像前面架构图，读请求目前是每秒 2000/s，两个从库各自抗了 1000/s 读请求，但是其中可能每秒 1800 次的读请求都是可以直接读缓存里的不怎么变化的数据的，</p>

<p>剩下落到数据库的只有 200 次；</p>

<br>


<h3>架构</h3>

<pre><code>                       |
                  高峰 1000/s
                       |
                       ↓
             {  nginx 负载均衡  }
               |       |       |
             300/s   300/s   300/s
               ↓       ↓       ↓
+——————+——→ { ECS1 } { ECS2 } { ECS3 } ←————+———————+
|      |        |                 |         |       |
|      |     500/s             500/s        |       |
|    100/s      ↓                 ↓        100/s    |
|      |    { 主库1 }          { 主库2 }      |      |
|      |        |                 |          |      |
|      |       同步              同步         |      |
900/s  |        ↓                 ↓          |    900/s
|      +——  { 从库1 }         { 从库2 } ——————+      |
|                                                   |
+——————————————————— { 缓存集群 } ———————————————————+
</code></pre>

<p>参考：<a href="http://www.php.cn/linux-417207.html">http://www.php.cn/linux-417207.html</a></p>

<br>


<br>


<h2>消息中间件集群</h2>

<p>上面对读的数据做了缓存，那么如果 写操作 比较多，那该怎么办，不可能一直加机器吧？</p>

<p>这里我们要引入 消息中间件集群，例如 RabbitMQ，他是非常好的做写请求异步化处理，实现 <strong>削峰填谷</strong> 的效果。</p>

<h3>架构</h3>

<pre><code>                       |
                  高峰 1000/s
                       |
                       ↓
             {  nginx 负载均衡  }
               |       |       |
             300/s   300/s   300/s
               |       |       |   +————————————————————————————+
               ↓       ↓       ↓   |                            |
+——————+——→ { ECS1 } { ECS2 } { ECS3 } ←————+———————+           |
|      |        |                 |         |       |     { 消息中间件 MQ }
|      |     500/s             500/s        |       |           |
|      |        |                 |         |       |    削峰填谷 100/s 请求慢慢写
|    100/s      ↓                 ↓        100/s    |           |
|      |    { 主库1 }          { 主库2 } ←————+——————+———————————+
|      |        |                 |          |      |
900/s  |        ↓                 ↓          |    900/s
|      +——  { 从库1 }         { 从库2 } ——————+      |
|                                                   |
+——————————————————— { 缓存集群 } ———————————————————+
</code></pre>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[前后端分离]]></title>
    <link href="https://TsaiKoga.github.com/blog/2019/04/14/qian-hou-duan-fen-chi/"/>
    <updated>2019-04-14T12:00:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2019/04/14/qian-hou-duan-fen-chi</id>
    <content type="html"><![CDATA[<h3>目录</h3>

<h4><a href="#1">一、模板引擎</a></h4>

<h4><a href="#2">二、单页面应用 或 API</a></h4>

<h4><a href="#3">三、前端 MVC 模式</a></h4>

<h4><a href="#4">四、前端 MVVM 模式</a></h4>

<h4><a href="#5">五、Nodejs 前后端分离</a></h4>

<h2 id="1"> 一、模板引擎</h2>


<ul>
<li>ERB: 前端渲染引擎，可以将后端传来的数据渲染注入到前端 HTML 中，也可以帮它叫做 ModelAndView（与 MVVM 的View-Model有区别，View-Model 是简化 Controller，有逻辑，负责 View 和 Model 的交互，而这里只是 Model 数据与 View 强绑定而已）；</li>
<li>JS: 除了实现一些前端效果，还需要用 ajax 发起对后台的请求；</li>
</ul>


<br>


<p>我还记得大三的时候，接触 Rails 框架，那时候 Rails 已经推出了 Assets 功能，
所有 CSS / JS 放在 assets/ 目录中，
html.erb 放在 views/ 目录；</p>

<p>然后通过编译，前端样式 assets/*.css 文件最终生成 application.css 放在了 public/ 目录中；
前端 JS assets/*.coffee 文件最终生成 application.js 也放在 public/ 目录下；
而 views/*.html.erb 文件编译后变成纯 html 调用；
目前 PHP 的 Laravel 框架也是如此；</p>

<br>


<p><strong>优点：</strong></p>

<p>形成的是带有动态数据的html，比较有利于SEO</p>

<p><strong>缺点：</strong></p>

<p>前后端内容实际上没有隔离；所以一般做 Rails 的人既要会前端，又要会后端；</p>

<p>前端需要搭建整个 Rails 或者 Laravel 环境；</p>

<br>




<h2 id="2"> 二、单页面应用 或 APP</h2>


<ul>
<li>单页面应用，其实就是所有请求都是 Ajax，这样解决了前面提到的模板引擎问题；</li>
<li>开发 APP，前端开发 H5、IOS、Android 等，后端只需要开发 API 返回前端需要的 json 数据；</li>
</ul>


<br>


<p>记得刚进入公司做后端 API 开发的时候，发现很多 vue 页面还是通过上诉模板方式与 Laravel 糅合在一起；
然后前端文件会存放在后端 Laravel 项目仓库中；
后来我们把他分割开，前端单独起一个项目仓库，然后服务器编译完再复制到后端 Laravel 项目下的 Public/目录中；
虽然还是没有完全分离开，但是前端已经不需要后端语法，直接就是访问后端 API 接口即可；</p>

<br>


<p><strong>优点：</strong></p>

<p>前端不需要懂后端的语法，不用学习像 ERB 这样的模板引擎语法，</p>

<p>只需要通过 ajax 请求后端，后端返回后对返回的 json 数据做处理；</p>

<p><strong>缺点：</strong></p>

<p>前端逻辑越来越重，越来越复杂，浏览器端 和 客户端 逻辑复杂；</p>

<p>不利于 SEO；</p>

<br>




<h2 id="3"> 三、前端 MVC 模式</h2>


<p>当初在大三的时候，在实验室使用 Extjs，那时候 Extjs 开始走 MVC 架构，
然后毕业答辩时提到前端 MVC，而老师竟然说前端没有 MVC ，后端才有 MVC，
这里就来讲讲什么是前端 MVC，</p>

<p>前端 MVC 和后端 MVC 类似，</p>

<ul>
<li>Model 用来存放数据对象；</li>
<li>View 用来呈现给用户，一般由 HTML/CSS/JS 组成；</li>
<li>Controller 用来从 View 获取事件和输入，并进行处理，相应更新后更新视图；</li>
</ul>


<br>


<p><strong>优点：</strong></p>

<p>分工明确，可以开发并行；</p>

<p><strong>缺点：</strong></p>

<p>Controller 要自己写，大量操作 DOM，页面渲染速度降低；
操作冗余，代码难以维护；</p>

<br>




<h2 id="4"> 四、前端 MVVM 模式：</h2>


<p>ViewModel 代替了 Controller；</p>

<ul>
<li>Model 用来存放数据对象；</li>
<li>View 用来呈现给用户，一般由 HTML/CSS/JS 组成；</li>
<li>View-Model：简化的 Controller，为 View 提供处理好的数据，view 绑定 view-model，视图与数据模型强耦合。数据的变化实时反映在 view 上，不需要手动处理；</li>
</ul>


<br>


<p>解决了 MVC 模式的痛点，Controller 大量逻辑被简化，不需要大量操作 DOM 了；
View 和 Model 没有直接联系，是通过 View-Model 进行交互的；</p>

<br>


<p><strong>优点：</strong></p>

<p>不需大量 DOM 操作，前端工作减少，逻辑清晰；</p>

<p><strong>缺点：</strong></p>

<p>不利于 SEO；</p>

<br>




<h2 id="5"> 五、Nodejs 前后端分离：</h2>


<p>我们公司已经使用了 Vue 作为前端，一个 MVVM 模式的框架，
但是，我们还是会经常遇到各种问题；</p>

<br>


<p><strong>例如：</strong></p>

<ol>
<li><p>页面设计逻辑例如循环构造呈现的 JSON 数据，要么得前端处理，要么后端处理，一般都是前端处理，前端所需的排序功能、筛选功能，
以及到了视图层的页面展现，也许都需要对接口所提供的数据进行二次处理。数据量一大便会浪费浏览器性能，也造成代码难以维护，很多时候无法通用；</p></li>
<li><p>多端产品 APP 会遇到接受格式不一致，像是 H5 可以接受 BOOLEAN 字段，而 IOS 端只能通过 1 或 0 改变；</p></li>
</ol>


<br>


<p>我们把原先的 MMVM 模式作为前端的 UI 层；
然后将 Nodejs 起的服务作为前端服务层，这个前端 Server 层需要部署在服务器上；</p>

<p>前端 UI 层：用来处理浏览器层的展现逻辑。通过 CSS 渲染样式，通过 JavaScript 添加交互功能；
前端 Server 层：处理路由、模板、数据获取、cookie 等，路由完全前端控制，所以无论是 单页面 还是 多页面，前端都可以自由调控；</p>

<br>


<p><strong>优点：</strong></p>

<p>解决第 1 点问题：后端可以只做自己的事情，数据直接成为 json 发送给前端，前端 Nodejs 处理 json 逻辑，
Node Server 层放在服务器上，不会造成浏览器资源浪费；</p>

<p>解决第 2 点问题：使用 Node Server 层可以支持多端开发需要的内容不一致问题，H5 能处理 BOOLEAN 值，IOS 无法处理的情况；</p>

<p><strong>缺点：</strong></p>

<p>前端所需要了解服务端编程，所学内容增加，是基于 Nodejs 的全栈开发；</p>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[服务器日志空间解决方案-外挂磁盘]]></title>
    <link href="https://TsaiKoga.github.com/blog/2019/03/28/fu-wu-qi-ri-zhi-kong-jian-jie-jue-fang-an-wai-gua-ci-pan/"/>
    <updated>2019-03-28T10:40:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2019/03/28/fu-wu-qi-ri-zhi-kong-jian-jie-jue-fang-an-wai-gua-ci-pan</id>
    <content type="html"><![CDATA[<p>最近 PHP 项目和 JAVA 项目放置在同一台服务器，但是 tomcat 日志过大导致空间爆满；
PHP 项目用户数量比较大，每天早上用户6点准时开单，这个时候突然登录不了了，我登录服务器发现日志已经占满了空间；</p>

<p>本身 Tomcat 项目已经做了切割日志，日志按天输出，但是有些 JAVA 开发人员，为了定位问题将大批量 SQL 写在日志上，缺忘了删除，导致某天的日志突然间过大，
达到了 15G 以上；</p>

<h2>方案：</h2>

<p>在删除日志之后，进过商量考虑到的解决方案有两个：</p>

<ol>
<li><p>使用 logrotate 对日志进行压缩限制；
这个方案觉得不合理，因为日志每天都要用来定位问题，如果压缩日志显得非常不方便，这个方案排除；</p></li>
<li><p>外挂磁盘，将日志导出到磁盘，这样磁盘满了也不影响应用；
外挂磁盘，然后日志目录建立软链接，指向外挂磁盘，这样日志满了，也不影响应用，只是无法继续生成日志而已，另一方面也方便定位日志；</p></li>
</ol>


<br>


<h2>步骤：</h2>

<h4>一、购买外挂磁盘，登录 Ubuntu 服务器，然后查看：</h4>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>df -h
</span></code></pre></td></tr></table></div></figure>


<p>目前这样看不到磁盘，因为还没挂载；</p>

<h4>二、查看磁盘：</h4>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>fdisk -l
</span><span class='line'>
</span><span class='line'>&gt; Disk /dev/vda: 40 GiB, 42949672960 bytes, 8388680 sectors
</span><span class='line'>&gt; ...
</span><span class='line'>&gt; Disk /dev/vdb: 100 GiB, ...
</span></code></pre></td></tr></table></div></figure>


<p>可以看到有另外的 100G 磁盘 /dev/vdb;</p>

<h4>三、建立新分区：</h4>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>fdisk /dev/vdb
</span></code></pre></td></tr></table></div></figure>


<ul>
<li>n = 创建新分区</li>
<li>1 = 成为磁盘上的首个分区</li>
<li>P = 直接创建主分区 （e是扩展分区，扩展分区无法直接用，需要在新建逻辑分区）</li>
</ul>


<p>我们选择 P
PS：如果之前是重新建立分区，要先 unmount 磁盘，然后对磁盘删除，选择 d，然后再创建主分区；</p>

<p>可以选择创建多少个分区，根据提示填写相应数字即可；</p>

<h4>四、格式化分区：</h4>

<p>创建完分区 /dev/vdb 之后 mkfs.ext4 直接格式话新建的分区就行</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>mkfs.ext4 /dev/vdb
</span></code></pre></td></tr></table></div></figure>


<h4>五、挂载：</h4>

<p>将磁盘挂载到 /opt 目录下，原有/opt 下的内容将会看不见，因为被覆盖住了，需要 unmount 才能看到；</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>mount /dev/vdb /opt
</span></code></pre></td></tr></table></div></figure>


<p>最后查看挂载磁盘</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>df -h
</span></code></pre></td></tr></table></div></figure>


<h4>六、创建软链接：</h4>

<p>已经挂载上了，我们在这里建立一个 tomcat-logs/ 目录，然后到 tomcat 下，把原有 logs/ 目录删除，
建立软链接 logs/ 指向 tomcat-logs/</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>mkdir -p /opt/tomcat-logs/
</span><span class='line'>ln -s /xxx/tomcat/logs /opt/tomcat-logs/
</span></code></pre></td></tr></table></div></figure>

]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[录单APP项目中的问题]]></title>
    <link href="https://TsaiKoga.github.com/blog/2018/10/28/lu-dan-appxiang-mu-zhong-de-wen-ti/"/>
    <updated>2018-10-28T15:46:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2018/10/28/lu-dan-appxiang-mu-zhong-de-wen-ti</id>
    <content type="html"><![CDATA[<h2>目录</h2>

<h4><a href="#1">分页重复数据问题</a></h4>

<h4><a href="#2">防止订单重复问题</a></h4>

<h4><a href="#3">订单号唯一问题</a></h4>

<h4><a href="#4">Web端报表系统使用导致APP端使用卡顿</a></h4>

<br/>


<br/>




<h2 id="1">分页重复数据问题</h2>


<hr />

<h4>背景：</h4>

<p>先解释一下，我们 app 项目中有一个录入订单模块，在这里每个店铺的工作人员会因为客户下单，在当天不停的进行录单；</p>

<p>这些订单按照当天的顺序形成一个单号，例如1，2，3，4&hellip; &hellip; 就这样；</p>

<p>app 中还有一个功能，就是插单，也就是如果有一张单据昨天忘记录入，那么可以添加插单时间到昨天，那么这张订单就插入了昨天；</p>

<p>但是，录单的工作人员有几个人，也就是同时有人会刷新这个页面，看到订单列表；</p>

<p>因为 app 是下拉刷新，加载第二页数据，并且是按照单据倒叙排列的，最先出现的是最新的单据；</p>

<p>这时候员工A如果开单到 25 号单据，然后再开第26的时候，员工B想要刷新第二页（按照每10张一页），那么本来应该看到的是15号单开始的第二页，</p>

<p>由于员工A完成26号单，这时候刷出来的是16号单开始的第二页，也就是25,24,23,&hellip;,16,16,15,14,&hellip;中间重单了；</p>

<br/>


<h4>解决方法：</h4>

<p>为了防止这种现象，必须在后台增加一个 <strong>过滤条件</strong>；</p>

<p>因为由时间排序，那么只要拿创建时间 <code>created_at</code> 与 前端传来查询时间 <code>search_at</code> 进行比较就可以筛选出第二页；</p>

<p>由于还有插单，所以插单的时间绝对不能覆盖创建时间 <code>created_at</code>，要有一个插单时间 <code>inserted_at</code>，这样排序用 <code>inserted_at</code> 来排序即可；</p>

<br/>


<br/>




<h2 id='2'>防止订单重复问题</h2>


<hr />

<h4>背景：</h4>

<p>由于这是一个给批发市场店铺的 app ；所以批发市场的店铺人员有限，但每天的订单数量又比较多，</p>

<p>这时候员工录入订单往往快速而又烦躁，对订单开单后可能会不停点击提交；虽然 IOS 端和 Android 端以对点击按钮做了屏蔽；</p>

<p>但是还是无法百分百杜绝一个单重复性提交；</p>

<p>这时候需要前端和后端配合一起防止同一张订单重复问题；</p>

<br/>


<h4>解决方法：</h4>

<p>前端给订单生成一个唯一码，一般用时间戳+随机数生成，这里我们用单词 exist_flag 代替；</p>

<p>然后前端发出请求，带上这个参数到后端；</p>

<p>后端接收到请求后首先将其用 redis 进行检验判断是否重复；</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='php'><span class='line'><span class="k">if</span> <span class="p">(</span><span class="nx">Redis</span><span class="o">::</span><span class="na">get</span><span class="p">(</span><span class="s1">&#39;orders:&#39;</span><span class="o">.</span> <span class="nv">$user_id</span> <span class="o">.</span> <span class="s1">&#39;-&#39;</span> <span class="o">.</span> <span class="nv">$exist_flag</span><span class="p">))</span> <span class="p">{</span>
</span><span class='line'>    <span class="k">return</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">fail</span><span class="p">(</span><span class="nx">self</span><span class="o">::</span><span class="na">ERROR_CODE</span><span class="p">,</span> <span class="s2">&quot;你还有订单正在进行中，请勿重复提交&quot;</span><span class="p">);</span>
</span><span class='line'><span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
</span><span class='line'>    <span class="nx">Redis</span><span class="o">::</span><span class="na">set</span><span class="p">(</span><span class="s1">&#39;orders:&#39;</span><span class="o">.</span> <span class="nv">$user_id</span> <span class="o">.</span> <span class="s1">&#39;-&#39;</span> <span class="o">.</span> <span class="nv">$exist_flag</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">180</span><span class="p">);</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>




<br/>


<br/>




<h2 id='3'>订单号唯一问题</h2>


<hr />

<h4>背景：</h4>

<p>正如前面所提到的，订单按照每日生成唯一的订单号1,2,3,4,5 &hellip;&hellip;；</p>

<p>这是针对当天唯一的号码，并且当天不能重复，并且生成单据最好能较快，不要因为顺序问题影响体验；</p>

<br/>


<h4>解决方法：</h4>

<p>利用联合唯一索引来解决；</p>

<p>例如单号字段为 <code>transaction_daily_serial</code>, 时间为 <code>inserted_at</code></p>

<p>这里使用插单是插入选择日期的最后单据，因为这样不会导致重新更改其他单号；</p>

<p>那么联合唯一索引：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">alter</span> <span class="k">table</span> <span class="n">transaction</span> <span class="k">add</span> <span class="k">unique</span> <span class="k">index</span> <span class="n">daily_sel_ins_at</span><span class="p">(</span><span class="n">transaction_daily_serial</span><span class="p">,</span> <span class="n">inserted_at</span><span class="p">);</span>
</span></code></pre></td></tr></table></div></figure>




<br/>


<br/>




<h2 id='4'>Web端报表系统使用导致APP端使用卡顿</h2>


<hr />

<h4>背景：</h4>

<p>APP 作为一个有点类似 ERP 的在线客户端，客户需要一些导出的Excel报表数据，包括（出入库数据，货品数据，订单总览）等等内容；</p>

<p>但由于数据内容非常庞大，并且客户不想要分批下载，他要一张excel展示所有时间段的数据；一开始数据量不多的时候，系统也没有为他们加时间限制；</p>

<p>后期，数据库数据量已经达到10G以上的时候，一段时间在业务高峰期出现 app 使用卡顿现象；</p>

<p>通过查询后台日志，我发现在这些卡顿时间都出现报表导出接口；</p>

<p>并且 APP 和 web 报表系统 是放在同一台服务器上；</p>

<br/>


<h4>解决方法：</h4>

<p>预想方案是有以下几个：</p>

<ol>
<li><p>分库【主从数据库】：因为 web 报表系统是查询数据，导出数据的系统，所以是只读系统，而 APP 是可读可写的；
分库可以保证 web 报表操作不影响 APP 手机端；</p></li>
<li><p>数据归档：将旧数据进行归档存储；</p></li>
<li><p>解决慢查询SQL</p></li>
<li><p>限制导出数据大小</p></li>
</ol>


<br/>


<p>由于公司项目较多，经费有限，无法再提供多一台服务器来专门用作 web 报表系统，所以方案一被取消；</p>

<p>数据归档虽然 CTO 答应采纳，但是当务之急是先解决目前问题，所以先从 方案三 和 方案四 下手；</p>

<p>方案三：通过阿里云的慢查询日志，定位到 SQL 语句，从而定位代码段；大部分慢查询可以通过添加联合索引解决；
但是一部分 smelly 的 SQL ORM 旧代码，就得重新编写优化；</p>

<p>方案四：根据客户需求和对应一个月的单据数量，给出最多只能下载一个月的数据；</p>

<br/>


<br/>

]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[利用 Mysql 日志及插件进行性能优化]]></title>
    <link href="https://TsaiKoga.github.com/blog/2018/05/12/li-yong-mysql-ri-zhi-ji-cha-jian-jin-xing-xing-neng-you-hua/"/>
    <updated>2018-05-12T17:37:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2018/05/12/li-yong-mysql-ri-zhi-ji-cha-jian-jin-xing-xing-neng-you-hua</id>
    <content type="html"><![CDATA[<h4><a href="#1">1. 数据库优化的目的</a></h4>

<h4><a href="#2">2. SQL及索引优化</a></h4>

<h5><a href="#2.1">一、慢查询日志设置</a></h5>

<h5><a href="#2.2">二、慢查询日志的分析工具</a></h5>

<h6><a href="#2.2.1">2.1 如何通过慢查询日志发现有问题的SQL</a></h6>

<h6><a href="#2.2.2">2.2 如何分析SQL查询</a></h6>

<h5><a href="#2.2">三、建立索引</a></h5>

<h6><a href="#2.3.1">3.1 如何选择合适的列建立索引：</a></h6>

<h6><a href="#2.3.2">3.2 索引的维护和优化—重复及冗余索引</a></h6>

<h6><a href="#2.3.3">3.3 删除不用索引</a></h6>

<h5><a href="#2.4">四、系统配置优化</a></h5>

<h4><a href="#3">3. 硬件要求</a></h4>

<h1 id='1'>数据库优化的目的：</h1>


<hr />

<h4>避免出现页面访问错误</h4>

<ul>
<li>由于数据库连接timeout产生页面5xx错误</li>
<li>由于慢查询造成页面无法加载</li>
<li>由于阻塞（加锁）造成数据无法提交</li>
</ul>


<br/>


<h4>增加数据库稳定性</h4>

<ul>
<li>很多数据库查询都是由低效的查询引起的</li>
</ul>


<br/>


<h4>优化用户体验</h4>

<ul>
<li>流畅页面访问速度</li>
<li>良好的网站功能体验</li>
</ul>


<br/>


<p><img src="https://TsaiKoga.github.com/images/posts/2018-05-12/mysql%E6%80%A7%E8%83%BD%E4%BC%98%E5%8C%96%E9%87%91%E5%AD%97%E5%A1%94.gif" title="mysql性能优化金字塔" alt="mysql性能优化金字塔" /></p>

<br/>


<br/>




<h1 id='2'>SQL及索引优化</h1>


<hr />

<h3>如何发现有问题的SQL？</h3>

<br/>




<h2 id='2.1'>一、慢查询日志设置</h2>


<hr />

<p>使用 Mysql 慢查日志对有效率问题的 SQL 进行监控</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="o">#</span> <span class="err">首先进入</span> <span class="n">mysql</span> <span class="err">的</span><span class="n">cli</span>
</span><span class='line'><span class="k">show</span> <span class="n">variables</span> <span class="k">like</span> <span class="ss">&quot;slow_query_log&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<p><img src="https://TsaiKoga.github.com/images/posts/2018-05-12/mysql_query_log.gif" title="mysql query log" alt="mysql query log" /></p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">set</span> <span class="k">global</span> <span class="n">slow_query_log_file</span><span class="o">=</span><span class="s1">&#39;/home/mysql/sql_log/mysql_slow.log&#39;</span> <span class="o">#</span> <span class="err">设置慢查询日志存储路径</span>
</span><span class='line'><span class="k">set</span> <span class="k">global</span> <span class="n">log_queries_now_using_indexes</span><span class="o">=</span><span class="k">on</span><span class="p">;</span>                        <span class="o">#</span> <span class="err">将没有索引的慢查询加入到慢查询日志中</span>
</span><span class='line'><span class="k">set</span> <span class="k">global</span> <span class="n">long_query_time</span><span class="o">=</span><span class="mi">1</span>                                        <span class="o">#</span> <span class="err">将大于</span><span class="mi">1</span><span class="n">s</span><span class="err">的设置到慢查询日志中</span>
</span><span class='line'><span class="k">Set</span> <span class="k">global</span> <span class="n">slow_query_log</span><span class="o">=</span><span class="k">on</span><span class="p">;</span>                                       <span class="o">#</span> <span class="err">开启慢查询日志记录</span>
</span></code></pre></td></tr></table></div></figure>


<h3>慢查询日志所包含的内容</h3>

<blockquote><p>执行 SQL 的主机信息</p>

<p>User@Host:root[root] @ localhost []</p>

<p>SQL的执行信息</p>

<p>Query_time: 0.000024 Lock_time: 0.0000 Rows_sent: 0  Rows_examined: 0</p>

<p>SQL执行时间</p>

<p>SET timestamp=1402389328</p>

<p>SQL的内容</p>

<p>select CONCAT(’storage engine:’,  @@storage_engine) as INFO;</p></blockquote>

<br/>


<br/>




<h2 id='2.2'>二、慢查询日志的分析工具：</h2>


<hr />

<h4>mysqldumpslow</h4>

<p><strong>mysqldumpslow</strong> [OPTS…] [LOGS…]    官方分析工具
返回count为查询次数，time为查询时间 ，rows为查询返回行数</p>

<p><img src="https://TsaiKoga.github.com/images/posts/2018-05-12/mysqldumpslow.gif" alt="mysql dump slow" /></p>

<br/>


<h4>pt-query-digest</h4>

<p>输出到文件：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="n">pt</span><span class="o">-</span><span class="n">query</span><span class="o">-</span><span class="n">digest</span> <span class="n">slow</span><span class="o">-</span><span class="n">log</span> <span class="o">&gt;</span> <span class="n">slow_log</span><span class="p">.</span><span class="n">report</span>
</span></code></pre></td></tr></table></div></figure>


<p>输出到数据库表：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="n">pt</span><span class="o">-</span><span class="n">query</span><span class="o">-</span><span class="n">digest</span> <span class="n">slow</span><span class="p">.</span><span class="n">log</span> <span class="o">-</span><span class="n">review</span> <span class="n">h</span><span class="o">=</span><span class="mi">127</span><span class="p">.</span><span class="mi">0</span><span class="p">.</span><span class="mi">0</span><span class="p">.</span><span class="mi">1</span><span class="p">,</span> <span class="n">D</span><span class="o">=</span><span class="n">test</span><span class="p">,</span> <span class="n">p</span><span class="o">=</span><span class="n">root</span><span class="p">,</span> <span class="n">P</span><span class="o">=</span><span class="mi">3306</span><span class="p">,</span> <span class="n">u</span><span class="o">=</span><span class="n">root</span><span class="p">,</span> <span class="n">t</span><span class="o">=</span><span class="n">query_review</span> <span class="c1">--create-reviewtable --review-history t=hostname_slow</span>
</span></code></pre></td></tr></table></div></figure>


<p><img src="https://TsaiKoga.github.com/images/posts/2018-05-12/pt-query-digest.gif" title="pt-query-digest" alt="pt-query-digest" />
<img src="https://TsaiKoga.github.com/images/posts/2018-05-12/pt-query-digest2.gif" title="pt-query-digest" alt="pt-query-digest" /></p>

<br/>


<br/>




<h2 id='2.2.1'>如何通过慢查询日志发现有问题的SQL</h2>


<hr />

<h4>1.查询次数多且每次查询占用时间长的SQL</h4>

<p>通常为 pt-query-digest 分析的前几个查询</p>

<h4>2.IO大的SQL</h4>

<p>注意 pt-query-digest 分析中的 Rows examine 项【扫描行数越多，IO越大】</p>

<h4>3.未命中索引的SQL</h4>

<p>注意 pt-query-digest 分析中Rows examines 和 Rows Send 的对比 【如果扫描行数 远大于 发送行数，要么没有索引，要么索引无效，导致类似于全表扫描】</p>

<p><img src="https://TsaiKoga.github.com/images/posts/2018-05-12/pt-query-digest3.gif" title="pt-query-digest" alt="pt-query-digest" /></p>

<br/>


<br/>




<h2 id='2.2.2'>如何分析SQL查询：</h2>


<hr />

<p>使用 explain 查询 SQL 的执行计划</p>

<p><img src="https://TsaiKoga.github.com/images/posts/2018-05-12/explain.gif" title="explain" alt="explain" /></p>

<p>table：                显示这一行数据属于哪张表</p>

<p>type：                 重要的列，显示连接使用了何种类型。从最好到最差的链接类型为const、eq_reg、ref、range、index 和 ALL</p>

<p>possible_keys：        显示可能应用这张表中的索引。如果为空，没有可能的索引。</p>

<p>Key：                  实际使用的索引。如果为NULL，则没有使用索引；</p>

<p>key_len：              使用索引的长度。在不损失精确性的情况下，长度越短越好；</p>

<p>ref：                  显示索引的哪一列被使用了，如果可能的话，是一个常数</p>

<p>rows：                 MYSQL认为必须检查的用来返回请求数据的行数</p>

<br/>


<h3>Max优化：</h3>

<p>对max字段使用索引，优化了explain的type；</p>

<h3>子查询的优化：</h3>

<p>通常情况下，把子查询优化成join，要注意是否一对多的关系，注意重复数据</p>

<h3>Limit优化：</h3>

<p>limit常用于分页操作，时常会伴随order by 从句使用，因此会使用 filesorts 这样会造成大量IO问题；</p>

<h4>优化步骤1：</h4>

<p>使用主键，或者索引列来进行Order by 操作；</p>

<h4>优化步骤2：</h4>

<p>记录上次返回主键，在下次查询使用主键过滤；【如果主键不是顺序增长的，有空缺，则返回的数量每页可能变少】，避免了数据量大时扫描过多的记录</p>

<br/>


<br/>




<h2 id="2.3">三、建立索引</h2>


<hr />

<h3 id="2.3.1"> 3.1 如何选择合适的列建立索引：</h3>


<hr />

<br/>


<p>1.在where从句，group by从句，order by从句，on从句出现的列；</p>

<p>2.索引字段越小越好；</p>

<p>3.离散度越大的列放在联合索引前面；</p>

<br/>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">select</span> <span class="o">*</span> <span class="k">from</span> <span class="n">payment</span> <span class="k">where</span> <span class="n">staff_id</span> <span class="o">=</span> <span class="mi">2</span> <span class="k">and</span> <span class="n">customer_id</span> <span class="o">=</span> <span class="mi">584</span><span class="p">;</span>
</span></code></pre></td></tr></table></div></figure>


<br/>


<p>是 index(staff_id, customer_id) 好？还是 index(customer_id, staff_id) 好？</p>

<br/>


<p>由于 customer_id 的离散度更大，所以应该使用 index(customer_id, staff_id)
那么如何知道离散程度：
可以通过一下查询：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">select</span> <span class="k">count</span><span class="p">(</span><span class="k">distinct</span> <span class="n">customer_id</span><span class="p">),</span> <span class="k">count</span><span class="p">(</span><span class="k">distinct</span> <span class="n">staff_id</span><span class="p">)</span> <span class="k">from</span> <span class="n">payment</span><span class="p">;</span>
</span></code></pre></td></tr></table></div></figure>


<p><img src="https://TsaiKoga.github.com/images/posts/2018-05-12/%E8%81%94%E5%90%88%E7%B4%A2%E5%BC%95%E7%A6%BB%E6%95%A3%E5%BA%A6.gif" alt="联合索引离散度" /></p>

<br/>


<p>得到staff_id比较集中，离散程度比较好，所以选择 customer_id 来作为联合索引前面的字段；</p>

<br/>




<h3 id="2.3.2"> 索引的维护和优化—重复及冗余索引</h3>


<p>重复的索引是指相同的列以相同的顺序建立的同类型的索引，如下表的 unique 索引中包含了 primary key 索引</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">create</span> <span class="k">table</span> <span class="n">test</span> <span class="p">(</span>
</span><span class='line'>  <span class="n">id</span> <span class="nb">int</span> <span class="k">not</span> <span class="k">null</span> <span class="k">primary</span> <span class="k">key</span><span class="p">,</span>
</span><span class='line'>  <span class="n">name</span> <span class="nb">varchar</span><span class="p">(</span><span class="mi">10</span><span class="p">)</span> <span class="k">not</span> <span class="k">null</span><span class="p">,</span>
</span><span class='line'>  <span class="n">title</span> <span class="nb">varchar</span><span class="p">(</span><span class="mi">50</span><span class="p">)</span> <span class="k">not</span> <span class="k">null</span><span class="p">,</span>
</span><span class='line'>  <span class="k">Unique</span><span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="n">id</span><span class="p">)</span>
</span><span class='line'><span class="p">)</span><span class="n">engine</span><span class="o">=</span><span class="n">innodb</span><span class="p">;</span>
</span></code></pre></td></tr></table></div></figure>


<p>使用pt-duplicate-key-checker工具检查重复及冗余索引</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="n">pt</span><span class="o">-</span><span class="n">duplicate</span><span class="o">-</span><span class="k">key</span><span class="o">-</span><span class="n">checker</span> <span class="o">-</span><span class="n">uroot</span> <span class="o">-</span><span class="n">p</span> <span class="o">-</span><span class="n">h127</span><span class="p">.</span><span class="mi">0</span><span class="p">.</span><span class="mi">0</span><span class="p">.</span><span class="mi">1</span>
</span></code></pre></td></tr></table></div></figure>




<br/>


<br/>




<h3 id="2.3.3"> 删除不用索引：</h3>


<p> mysql没有记录索引使用情况，但在PerconMysql，MariaDB中有INDEX_STATISTICS表来查看哪些索引未使用，但在mysql中目前只能通过慢查询日志来配合 pt-index-usage 工具来进行索引使用情况分析；</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="n">pt</span><span class="o">-</span><span class="k">index</span><span class="o">-</span><span class="k">usage</span> <span class="o">-</span><span class="n">uroot</span> <span class="o">-</span><span class="n">p</span> <span class="n">mysql</span><span class="o">-</span><span class="n">slow</span><span class="p">.</span><span class="n">log</span>
</span></code></pre></td></tr></table></div></figure>




<h2 id='2.4'>四、系统配置优化：</h2>


<hr />

<p>Mysql 配置文件-常用参数说明</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="n">Innodb_buffer_pool_size</span>
</span></code></pre></td></tr></table></div></figure>


<p>配置innodb的缓冲池，如果数据库中只有innodb表，则推荐配置量为总内存的75%；</p>

<br/>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="n">innodb_buffer_pool_instances</span>
</span></code></pre></td></tr></table></div></figure>


<p>可以控制缓冲池的个数，默认一个缓冲池</p>

<br/>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="n">innodb_log_buffer_size</span>
</span></code></pre></td></tr></table></div></figure>


<p>Innodb log 缓冲的大小，由于日志最长每秒就会刷新所以一般不用太大；</p>

<br/>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="n">innodb_flush_log_at_trx_commit</span>
</span></code></pre></td></tr></table></div></figure>


<p>关键参数，对 innodb 影响很大。默认值为1，可以取0，1，2三个值，一般建议设为2，如果安全性要求高则使用默认值1；</p>

<br/>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="n">innodb_read_io_threads</span>
</span><span class='line'><span class="n">Innodb_write_io_threads</span>
</span></code></pre></td></tr></table></div></figure>


<p>读写io进程数，默认为4；</p>

<br/>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="n">innodb_file_per_table</span>
</span></code></pre></td></tr></table></div></figure>


<p>关键参数，控制 Innodb 每个表使用独立的表空间，默认为OFF，也就是所有表会建立在共享表空间中，IO 会形成瓶颈；
建议设置为 ON，这样每个使用独立的共享表空间；</p>

<br/>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="n">Innodb_stats_on_metadata</span>
</span></code></pre></td></tr></table></div></figure>


<p>决定 mysql 什么情况下会刷新 innodb 表的统计信息；</p>

<p>上述信息可以使用 Per Configuration Wizard 配置</p>

<br/>


<br/>




<h1 id="3">硬件要求：</h1>


<hr />

<p>如何选择CPU</p>

<ol>
<li><p>Mysql一些工作只能用单核CPU：   SQL语句执行，Replicate；</p></li>
<li><p>Mysql对核数并不是越多越好：mysql5.5 不要超过32核；</p></li>
</ol>

]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[利用select union join 解决分页与排序的矛盾]]></title>
    <link href="https://TsaiKoga.github.com/blog/2017/10/02/li-yong-select-union-join-jie-jue-fen-ye-yu-pai-xu-de-mao-dun/"/>
    <updated>2017-10-02T18:34:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2017/10/02/li-yong-select-union-join-jie-jue-fen-ye-yu-pai-xu-de-mao-dun</id>
    <content type="html"><![CDATA[<p>刚入职新公司的时候，被数据库的设计吓了一跳；要在一个有缺陷的数据库上解决数据量很大而导致的查询速度慢问题。</p>

<p>首先，先来讲一下这个场景，这是一个APP的交易页面，他要显示的列表信息是衣服的款号，在这款号下面有这个款的几个SKU
（颜色尺码），以及SKU对应的销售量和交易额。</p>

<p><img src="https://TsaiKoga.github.com/images/posts/2017-10-02/mysql-view.jpg" title="视图场景" alt="视图场景" /></p>

<p>然后，数据库中有三个单据表：开单OrderCreate，改单OrderModification，退货单ReturnGoods；
这三张表各有三个子表 开单子表OrderCreateGoodsSku，改单子表OrderModificationGoodsSku，退货子表ReturnGoodsSku；
这些子表都有对应的goods_count和goods_price，分别代表着交易数量和单价；他们都对应这一张交易单表 transaction；</p>

<p>所以，销售量是（开单+改单-退货）的goods_count，
交易额是（开单goods_count * 开单goods_price + 改单goods_count * 改单goods_price &ndash; 退货goods_count * 退货goods_price)
当然，由于还要显示颜色尺码以及款号，我们还需要去join 有这些字段的表才行。</p>

<p>一开始入职时，觉得这三张表其实字段基本相同，可以将它放在一张表中，使用 type 字段做区分，类似于 ruby on rails 中的单表继承；
这样，算销量 和 销售价 就从这张表出发 join sku 就可以了，这样可比分三张要快；</p>

<p>后来数据量比较大时，也会想，这样也许是为了分表，减少数据在单张表的数量；
transaction 做为主表，分别被 create_order 开单、modification_order 改单 和 return_goods 退货关联；
不过分表可能要根据业务逻辑，如果是页面中有对单独类型显示，可以用这种分法，不过一般还是对时间的依赖性比较强；</p>

<p>回过头来，我们继续看看这三张主要单据：</p>

<p>由于全部时间单据实在太多，一次性找出来构造成所需要的形式也很耗时；再者，随着时间推移，单据越来越多，这查询速度就更加不能接受了。</p>

<p>所以应该使用分页解决。但是这里还有一个需求，就是要根据交易额和销售量排序。也就是三张表查出的数据进行计算后的结果集进行排序。</p>

<p>但是这样就无法真正意义上的分页了，所以有没有办法 <strong>在排序后，取出结果集前进行分页</strong> 呢？</p>

<p>CTO建议使用视图。</p>

<h3>什么是视图</h3>

<hr />

<p>视图是一个 <strong>虚拟表</strong>，其内容由查询定义。同真实的表一样，视图包含一系列带有名称的列和行数据。
但是，视图并不在数据库中以存储的数据值集形式存在。行和列数据来自由定义视图的查询所引用的表，并且在 <strong>引用视图时动态生成</strong>。</p>

<p>视图只是一段逻辑。</p>

<h3>使用视图解决排序与分页的矛盾</h3>

<p>现在我们只需要把三张子表的内容全部 union 成一张虚拟表就行了</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">CREATE</span> <span class="n">ALGORITHM</span><span class="o">=</span><span class="n">UNDEFINED</span> <span class="k">DEFINER</span><span class="o">=`</span><span class="n">juniu</span><span class="o">`@`%`</span> <span class="k">SQL</span> <span class="k">SECURITY</span> <span class="k">DEFINER</span> <span class="k">VIEW</span> <span class="o">`</span><span class="n">juniu_transfer</span><span class="o">`</span> <span class="k">AS</span>
</span><span class='line'><span class="p">(</span><span class="k">select</span> <span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">goods_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_count</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">goods_count</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_price</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">goods_price</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_sku_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">goods_sku_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">store_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">store_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">customer_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">customer_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">seller_user_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">seller_user_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">operate_user_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">operate_user_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="k">timestamp</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="k">timestamp</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">transaction_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">transaction_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">dev_flag</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">dev_flag</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">deleted_at</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">deleted_at</span><span class="o">`</span>
</span><span class='line'> <span class="k">from</span> <span class="o">`</span><span class="n">juniu_order_create_goods_sku</span><span class="o">`</span><span class="p">)</span>
</span><span class='line'><span class="k">union</span> <span class="k">all</span>
</span><span class='line'><span class="p">(</span><span class="k">select</span> <span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">goods_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_count_diff</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">goods_count_diff</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_price</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">goods_price</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_sku_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">goods_sku_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">store_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">store_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">customer_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">customer_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">seller_user_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">seller_user_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">operate_user_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">operate_user_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="k">timestamp</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="k">timestamp</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">transaction_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">transaction_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">dev_flag</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">dev_flag</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">deleted_at</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">deleted_at</span><span class="o">`</span>
</span><span class='line'>  <span class="k">from</span> <span class="o">`</span><span class="n">juniu_order_modification_goods_sku</span><span class="o">`</span><span class="p">)</span>
</span><span class='line'><span class="k">union</span> <span class="k">all</span>
</span><span class='line'><span class="p">(</span><span class="k">select</span> <span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">goods_id</span><span class="o">`</span><span class="p">,(</span><span class="o">-</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span> <span class="o">*</span> <span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_count</span><span class="o">`</span><span class="p">)</span> <span class="k">AS</span> <span class="o">`-</span><span class="mi">1</span><span class="o">*</span><span class="n">goods_count</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_price</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">goods_price</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">goods_sku_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">goods_sku_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">store_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">store_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">customer_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">customer_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">seller_user_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">seller_user_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">operate_user_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">operate_user_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="k">timestamp</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="k">timestamp</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">transaction_id</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">transaction_id</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">dev_flag</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">dev_flag</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">.</span><span class="o">`</span><span class="n">deleted_at</span><span class="o">`</span> <span class="k">AS</span> <span class="o">`</span><span class="n">deleted_at</span><span class="o">`</span>
</span><span class='line'>  <span class="k">from</span> <span class="o">`</span><span class="n">juniu_return_goods_sku</span><span class="o">`</span><span class="p">);</span>
</span></code></pre></td></tr></table></div></figure>


<p>这就是创建的视图，它有了我们想要的goods_count和goods_price，并且将ReturnGoodsSku的goods_count改为了负数，这样我们可以一次性SUM起来，
实现交易额和销量的运算；</p>

<p>然后在取出所有数据之前对结果集进行排序。最后通过top或limit取出来；</p>

<p>你也可以先建立这个视图的Model，然后就可以通过ORM来获取结果集。</p>

<p>最后，说说效果，其实效果不能接受，因为三张表的数据 union all 后数据量太庞大，导致加载速度还是非常非常慢，union all时间实在太长了；
mysql 视图又无法使用索引；所以鱼与熊掌不可得兼。</p>

<h3>使用 select union join as 解决排序与分页的矛盾</h3>

<p>那么该怎么办呢，架构师提议尽量利用索引，可以试图把union all的数据减少，也就是先用 where 进行筛选然后再 union all；
然后对这些已经筛选并且合并的数据进行 join 关联操作（这样可以 <strong>大大减少 join 关联的内容</strong>）；
最后再次将他们 select 出来：</p>

<p>其实分表后也是这样来汇集所有分表的数据到一张表的，算是分表的一种查询操作吧：</p>

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</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">SELECT</span>
</span><span class='line'>  <span class="k">g</span><span class="p">.</span><span class="n">goods_id</span><span class="p">,</span>
</span><span class='line'>  <span class="k">SUM</span><span class="p">(</span><span class="n">t</span><span class="p">.</span><span class="n">saleVolumn</span><span class="p">)</span> <span class="k">AS</span> <span class="n">saleVolumn</span>
</span><span class='line'><span class="k">FROM</span>
</span><span class='line'>  <span class="n">juniu_goods</span> <span class="k">AS</span> <span class="k">g</span>
</span><span class='line'><span class="k">LEFT</span> <span class="k">JOIN</span> <span class="p">(</span>
</span><span class='line'>  <span class="p">(</span>
</span><span class='line'>      <span class="k">SELECT</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">goods_id</span> <span class="k">AS</span> <span class="n">goods_id</span><span class="p">,</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">goods_count</span> <span class="k">AS</span> <span class="n">goods_count</span><span class="p">,</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">goods_price</span> <span class="k">AS</span> <span class="n">goods_price</span><span class="p">,</span>
</span><span class='line'>          <span class="k">sum</span><span class="p">(</span>
</span><span class='line'>              <span class="k">c</span><span class="p">.</span><span class="n">goods_count</span> <span class="o">*</span> <span class="k">c</span><span class="p">.</span><span class="n">goods_price</span>
</span><span class='line'>          <span class="p">)</span> <span class="k">AS</span> <span class="n">saleVolumn</span><span class="p">,</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">goods_sku_id</span> <span class="k">AS</span> <span class="n">goods_sku_id</span><span class="p">,</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">store_id</span> <span class="k">AS</span> <span class="n">store_id</span><span class="p">,</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">customer_id</span> <span class="k">AS</span> <span class="n">customer_id</span><span class="p">,</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">seller_user_id</span> <span class="k">AS</span> <span class="n">seller_user_id</span><span class="p">,</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">operate_user_id</span> <span class="k">AS</span> <span class="n">operate_user_id</span><span class="p">,</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span> <span class="k">TIMESTAMP</span> <span class="k">AS</span> <span class="k">TIMESTAMP</span><span class="p">,</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">transaction_id</span> <span class="k">AS</span> <span class="n">transaction_id</span><span class="p">,</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">dev_flag</span> <span class="k">AS</span> <span class="n">dev_flag</span><span class="p">,</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">deleted_at</span> <span class="k">AS</span> <span class="n">deleted_at</span><span class="p">,</span>
</span><span class='line'>          <span class="s1">&#39;create&#39;</span> <span class="k">AS</span> <span class="n">order_type</span><span class="p">,</span>
</span><span class='line'>          <span class="mi">0</span> <span class="k">AS</span> <span class="n">return_count</span>
</span><span class='line'>      <span class="k">FROM</span>
</span><span class='line'>          <span class="n">juniu_order_create_goods_sku</span> <span class="k">AS</span> <span class="k">c</span>
</span><span class='line'>      <span class="k">WHERE</span>
</span><span class='line'>          <span class="k">c</span><span class="p">.</span><span class="n">store_id</span> <span class="o">=</span> <span class="mi">651</span>
</span><span class='line'>      <span class="k">GROUP</span> <span class="k">BY</span>
</span><span class='line'>          <span class="n">goods_id</span>
</span><span class='line'>  <span class="p">)</span>
</span><span class='line'>  <span class="k">UNION</span> <span class="k">ALL</span>
</span><span class='line'>      <span class="p">(</span>
</span><span class='line'>          <span class="k">SELECT</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">goods_id</span> <span class="k">AS</span> <span class="n">goods_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">goods_count_diff</span> <span class="k">AS</span> <span class="n">goods_count_diff</span><span class="p">,</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">goods_price</span> <span class="k">AS</span> <span class="n">goods_price</span><span class="p">,</span>
</span><span class='line'>              <span class="k">sum</span><span class="p">(</span>
</span><span class='line'>                  <span class="n">m</span><span class="p">.</span><span class="n">goods_count_diff</span> <span class="o">*</span> <span class="n">m</span><span class="p">.</span><span class="n">goods_price</span>
</span><span class='line'>              <span class="p">)</span> <span class="k">AS</span> <span class="n">saleVolumn</span><span class="p">,</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">goods_sku_id</span> <span class="k">AS</span> <span class="n">goods_sku_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">store_id</span> <span class="k">AS</span> <span class="n">store_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">customer_id</span> <span class="k">AS</span> <span class="n">customer_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">seller_user_id</span> <span class="k">AS</span> <span class="n">seller_user_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">operate_user_id</span> <span class="k">AS</span> <span class="n">operate_user_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span> <span class="k">TIMESTAMP</span> <span class="k">AS</span> <span class="k">TIMESTAMP</span><span class="p">,</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">transaction_id</span> <span class="k">AS</span> <span class="n">transaction_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">dev_flag</span> <span class="k">AS</span> <span class="n">dev_flag</span><span class="p">,</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">deleted_at</span> <span class="k">AS</span> <span class="n">deleted_at</span><span class="p">,</span>
</span><span class='line'>              <span class="s1">&#39;modification&#39;</span> <span class="k">AS</span> <span class="n">order_type</span><span class="p">,</span>
</span><span class='line'>              <span class="mi">0</span> <span class="k">AS</span> <span class="n">return_count</span>
</span><span class='line'>          <span class="k">FROM</span>
</span><span class='line'>              <span class="n">juniu_order_modification_goods_sku</span> <span class="k">AS</span> <span class="n">m</span>
</span><span class='line'>          <span class="k">WHERE</span>
</span><span class='line'>              <span class="n">m</span><span class="p">.</span><span class="n">store_id</span> <span class="o">=</span> <span class="mi">651</span>
</span><span class='line'>          <span class="k">GROUP</span> <span class="k">BY</span>
</span><span class='line'>              <span class="n">goods_id</span>
</span><span class='line'>      <span class="p">)</span>
</span><span class='line'>  <span class="k">UNION</span> <span class="k">ALL</span>
</span><span class='line'>      <span class="p">(</span>
</span><span class='line'>          <span class="k">SELECT</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">goods_id</span> <span class="k">AS</span> <span class="n">goods_id</span><span class="p">,</span>
</span><span class='line'>              <span class="p">(</span><span class="o">-</span> <span class="mi">1</span> <span class="o">*</span> <span class="n">r</span><span class="p">.</span><span class="n">goods_count</span><span class="p">)</span> <span class="k">AS</span> <span class="n">goods_count</span><span class="p">,</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">goods_price</span> <span class="k">AS</span> <span class="n">goods_price</span><span class="p">,</span>
</span><span class='line'>              <span class="k">sum</span><span class="p">(</span><span class="o">-</span> <span class="mi">1</span> <span class="o">*</span> <span class="n">r</span><span class="p">.</span><span class="n">goods_price</span><span class="p">)</span> <span class="k">AS</span> <span class="n">saleVolumn</span><span class="p">,</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">goods_sku_id</span> <span class="k">AS</span> <span class="n">goods_sku_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">store_id</span> <span class="k">AS</span> <span class="n">store_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">customer_id</span> <span class="k">AS</span> <span class="n">customer_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">seller_user_id</span> <span class="k">AS</span> <span class="n">seller_user_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">operate_user_id</span> <span class="k">AS</span> <span class="n">operate_user_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span> <span class="k">TIMESTAMP</span> <span class="k">AS</span> <span class="k">TIMESTAMP</span><span class="p">,</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">transaction_id</span> <span class="k">AS</span> <span class="n">transaction_id</span><span class="p">,</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">dev_flag</span> <span class="k">AS</span> <span class="n">dev_flag</span><span class="p">,</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">deleted_at</span> <span class="k">AS</span> <span class="n">deleted_at</span><span class="p">,</span>
</span><span class='line'>              <span class="s1">&#39;return&#39;</span> <span class="k">AS</span> <span class="n">order_type</span><span class="p">,</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">goods_count</span> <span class="k">AS</span> <span class="n">return_count</span>
</span><span class='line'>          <span class="k">FROM</span>
</span><span class='line'>              <span class="n">juniu_return_goods_sku</span> <span class="k">AS</span> <span class="n">r</span>
</span><span class='line'>          <span class="k">WHERE</span>
</span><span class='line'>              <span class="n">r</span><span class="p">.</span><span class="n">store_id</span> <span class="o">=</span> <span class="mi">651</span>
</span><span class='line'>          <span class="k">GROUP</span> <span class="k">BY</span>
</span><span class='line'>              <span class="n">goods_id</span>
</span><span class='line'>      <span class="p">)</span>
</span><span class='line'><span class="p">)</span> <span class="k">AS</span> <span class="n">t</span> <span class="k">ON</span> <span class="k">g</span><span class="p">.</span><span class="n">goods_id</span> <span class="o">=</span> <span class="n">t</span><span class="p">.</span><span class="n">goods_id</span>
</span><span class='line'><span class="k">WHERE</span>
</span><span class='line'>  <span class="k">g</span><span class="p">.</span><span class="n">store_id</span> <span class="o">=</span> <span class="mi">651</span>
</span><span class='line'><span class="k">GROUP</span> <span class="k">BY</span>
</span><span class='line'>  <span class="k">g</span><span class="p">.</span><span class="n">goods_id</span>
</span><span class='line'><span class="k">ORDER</span> <span class="k">BY</span>
</span><span class='line'>  <span class="n">saleVolumn</span> <span class="k">DESC</span>
</span><span class='line'><span class="k">LIMIT</span> <span class="mi">0</span><span class="p">,</span>
</span><span class='line'> <span class="mi">20</span>
</span></code></pre></td></tr></table></div></figure>


<p>这个效果拔群！</p>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[Mysql索引]]></title>
    <link href="https://TsaiKoga.github.com/blog/2017/10/02/mysqlsuo-yin/"/>
    <updated>2017-10-02T18:05:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2017/10/02/mysqlsuo-yin</id>
    <content type="html"><![CDATA[<h4><a href="#1">1.索引的优缺点原因</a></h4>

<h5><a href="#1.1">1.1为什么添加索引，查询速度变快</a></h5>

<h5><a href="#1.2">1.2为什么添加上索引，速度会变慢</a></h5>

<h4><a href="#2">2.索引的类别</a></h4>

<h5><a href="#2.1">2.1主键索引</a></h5>

<h5><a href="#2.2">2.2唯一索引</a></h5>

<h5><a href="#2.3">2.3普通索引</a></h5>

<h5><a href="#2.4">2.4多列索引</a></h5>

<h5><a href="#2.5">2.5全文索引</a></h5>

<h4><a href="#3">3.加索引情况</a></h4>

<h5><a href="#3.1">3.1 关键词</a></h5>

<h5><a href="#3.2">3.2 小技巧</a></h5>

<h4><a href="#4">4.索引生成文件</a></h4>

<h5><a href="#4.1">4.1 索引文件</a></h5>

<br/>


<p>之前一直对索引没有很清晰的认识，每次一创建表时，就给外键加索引，只知道索引提高mysql搜索效率；
前阵子查阅了很多资料，有了比较清晰的认识，现在给出如下总结：</p>

<br/>




<h2 id='1'>索引的优缺点原因</h2>


<hr />

<h3 id='1.1'>为什么添加索引，查询速度变快</h3>


<hr />

<p>计算机查找某一条记录，如果不加索引，会在整个表中一条一条比较，将匹配的记录加入 <strong>结果集</strong>，很多人说这样会很慢，加了索引就快了。</p>

<p>为什么？</p>

<p>计算机先在索引列表中找到记录的 <strong>位置</strong>，既 <strong>rowid</strong>，然后直接去表中的对应位置取出记录，我就不明白了，查找索引列表难道不需要一条一条的匹配？计算机又不会出现说，看索引列表比直接看表中的记录要快，先在索引列表中找到记录对应的 rowid 也是要遍历的？难道不是同样的吗？</p>

<br/>


<p>Mysql 索引主要两种：</p>

<br/>


<p><strong>1.BTree</strong>
取中间数作为根，比根小的数再取中间数放左边，大数放右边作为右边树叶；
时间复杂度就是log2(n)；</p>

<br/>


<p><strong>2.Hash</strong>
key-value 保存;
时间复杂度是(n);
缺点：不支持范围查询，只能指定查询；</p>

<br/>


<br/>




<h3 id='1.2'>为什么添加上索引，速度会变慢</h3>


<hr />

<ol>
<li><p>DML 耗时：根据上面的回答，添加索引会 <strong>构建 BTree </strong>，建立 <strong>索引都需要维护</strong>，你  <strong>创建、插入或删除</strong> 记录，都要重新构建部分 BTree；
【所以唯一性太差的字段不适合创建索引；字段频繁变化的字段也不适合创建索引】</p></li>
<li><p>消耗磁盘空间；</p></li>
</ol>


<br/>


<br/>




<h2 id='2'>索引的类别</h2>


<hr />

<h3 id='2.1'>主键索引</h3>


<hr />

<p>添加PRIMARY KEY（主键索引）</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">ALTER</span> <span class="k">TABLE</span> <span class="o">`</span><span class="k">table_name</span><span class="o">`</span> <span class="k">ADD</span> <span class="k">PRIMARY</span> <span class="k">KEY</span> <span class="p">(</span> <span class="o">`</span><span class="k">column</span><span class="o">`</span> <span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>




<br/>


<h3 id='2.2'>唯一索引</h3>


<hr />

<p>添加UNIQUE(唯一索引)</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">ALTER</span> <span class="k">TABLE</span> <span class="o">`</span><span class="k">table_name</span><span class="o">`</span> <span class="k">ADD</span> <span class="k">UNIQUE</span> <span class="p">(</span> <span class="o">`</span><span class="k">column</span><span class="o">`</span> <span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p><strong>唯一索引中 null 不代表重复，可以有多个 null；</strong></p>

<br/>


<h3 id='2.3'>普通索引</h3>


<hr />

<p>添加INDEX(普通索引)</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">ALTER</span> <span class="k">TABLE</span> <span class="o">`</span><span class="k">table_name</span><span class="o">`</span> <span class="k">ADD</span> <span class="k">INDEX</span> <span class="n">index_name</span> <span class="p">(</span> <span class="o">`</span><span class="k">column</span><span class="o">`</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>




<br/>


<h3 id='2.4'>多列索引</h3>


<hr />

<p>也叫联合索引；
添加多列索引</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">ALTER</span> <span class="k">TABLE</span> <span class="o">`</span><span class="k">table_name</span><span class="o">`</span> <span class="k">ADD</span> <span class="k">INDEX</span> <span class="n">index_name</span> <span class="p">(</span> <span class="o">`</span><span class="n">column1</span><span class="o">`</span><span class="p">,</span><span class="o">`</span><span class="n">column2</span><span class="o">`</span><span class="p">,</span> <span class="o">`</span><span class="n">column3</span><span class="o">`</span> <span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>一般用在 where 几个字段，并且使用频繁的语句；
当使用联合索引后，第一个 column1 将是一级目录，所以不用单独给它做索引，因为他已经是单独的索引了；</p>

<p>第二个 column2 是二级目录索引，所以如果你也可以增加多一个单独索引，因为不可能直接使用二级目录的；</p>

<br/>


<h3 id='2.5'>全文索引</h3>


<hr />

<p>添加FULLTEXT(全文索引)</p>

<p>全文索引只能在 <strong>MYISAM</strong> 引擎中使用：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">ALTER</span> <span class="k">TABLE</span> <span class="o">`</span><span class="k">table_name</span><span class="o">`</span> <span class="k">ADD</span> <span class="n">FULLTEXT</span> <span class="p">(</span><span class="o">`</span><span class="k">column</span><span class="o">`</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<h4>如何使用：</h4>

<p>在MySQL中创建全文索引之后，现在就该了解如何使用了。众所周知，在数据库中进行模糊查询是使用LIKE关键字进行查询，例如：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">SELECT</span> <span class="o">*</span> <span class="k">FROM</span> <span class="n">article</span> <span class="k">WHERE</span> <span class="n">content</span> <span class="k">LIKE</span> <span class="s1">&#39;%查询字符串%&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>那么，我们使用全文索引也是这样用的吗？当然不是，我们必须使用特有的语法才能使用全文索引进行查询。例如，我们想要在article表的title和content列中全文检索指定的查询字符串，可以如下编写SQL语句：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">SELECT</span> <span class="o">*</span> <span class="k">FROM</span> <span class="n">article</span> <span class="k">WHERE</span> <span class="k">MATCH</span><span class="p">(</span><span class="n">title</span><span class="p">,</span> <span class="n">content</span><span class="p">)</span> <span class="n">AGAINST</span><span class="p">(</span><span class="s1">&#39;查询字符串&#39;</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>PS: 全文索引并不是所有文本都加索引，而是通过“停止词”；
对一些常用词，没什么特殊含义的词（a, the, at, which, want&hellip;）不加索引，这些词叫做停止词；</p>

<br/>




<h3 id='2.6'>查询、修改、删除索引</h3>


<hr />

<p>1.查询
desc 表名;【该方法的缺点，不能显示索引名】</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">show</span> <span class="k">index</span> <span class="k">from</span> <span class="err">表名</span><span class="p">;</span>
</span><span class='line'><span class="k">show</span> <span class="n">keys</span> <span class="k">from</span> <span class="err">表名</span><span class="p">;</span>
</span></code></pre></td></tr></table></div></figure>


<br/>


<p>2.删除</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">alter</span> <span class="k">table</span> <span class="err">表名</span> <span class="k">drop</span> <span class="k">index</span> <span class="err">索引名</span><span class="p">;</span>
</span><span class='line'><span class="err">如果删除主键索引：</span>
</span><span class='line'><span class="k">alter</span> <span class="k">table</span> <span class="err">表名</span> <span class="k">drop</span> <span class="k">primary</span> <span class="k">key</span><span class="p">;</span>
</span></code></pre></td></tr></table></div></figure>


<br/>


<p>3.修改</p>

<p>先删除，再重新创建；</p>

<br/>


<br/>




<p><h2 id='3'>加索引的情况</h3></p>

<p><h3 id='3.1'> 关键词 </h3>
一些关键词代表可能会经常用到索引，具体还是要把 SQL 语句从程序中 debug 出来，
然后在 mysql 中查看用 explain 是否有用到该索引：</p>

<p>1.分组字段：
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">group</span> <span class="k">by</span>
</span></code></pre></td></tr></table></div></figure>
很多人觉得不会用到，其实会用到的；
按照 explain 可以看出单独对驱动表使用 group by，mysql 计划是会使用索引的；
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">explain</span>
</span><span class='line'><span class="k">select</span> <span class="o">*</span>
</span><span class='line'><span class="k">from</span> <span class="n">juniu_return_goods_sku</span>
</span><span class='line'><span class="k">group</span> <span class="k">by</span> <span class="n">juniu_return_goods_sku</span><span class="p">.</span><span class="n">goods_id</span>
</span></code></pre></td></tr></table></div></figure>
这里返回使用了索引，并且不会 用到 using temporary;
所以加了索引，用 explain 验证一下即可；</p>

<p>2.排序字段：
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">order</span> <span class="k">by</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>3.统计字段，【注意运算不会用索引，例如:SUM, YEAR】：
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">select</span> <span class="k">MAX</span><span class="p">()</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>4.主键外键字段：
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">JOIN</span><span class="p">()</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>还有要注意无效索引：</p>

<p>1.运算字段：
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">WHERE</span> <span class="n">DATE_FORMATE</span><span class="p">(</span><span class="n">created_at</span><span class="p">,</span> <span class="s1">&#39;%Y/%m%/d&#39;</span><span class="p">)</span> <span class="o">=</span> <span class="s1">&#39;2018-05-12&#39;</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>2.Like语句：
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">like</span> <span class="ss">&quot;%aaa%&quot;</span> <span class="o">//</span> <span class="err">不会用到索引</span>
</span><span class='line'><span class="k">like</span> <span class="ss">&quot;aaa%&quot;</span> <span class="o">//</span> <span class="err">会用到索引</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>3.含有NULL值的列【注意：给默认值】</p>

<p>4.NOT IN语句【注意：可以改成 NOT EXISTS】：
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">WHERE</span> <span class="n">id</span> <span class="k">NOT</span> <span class="k">IN</span> <span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">);</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>5.OR 语句：
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">WHERE</span> <span class="n">id</span> <span class="o">=</span> <span class="mi">1</span> <span class="k">OR</span> <span class="n">id</span> <span class="o">=</span> <span class="mi">2</span><span class="p">;</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>它先对日期值使用 DATE_FORMATE 方法，所以索引无效；</p>

<p><br/>
<br/></p>

<p><h3 id='3.2'> 小技巧 </h3></p>

<ol>
<li><p>在使用 <strong>group by</strong> 分组查询时，默认分组后，还会排序，可能会降低速度；
例如：在一张表中对一个索引字段进行 group by ，explain后发现他不会使用索引，但是 extra 中有 <strong>Using filesort</strong>；
解决：group by 后面加上 <strong>order by null</strong>;</p></li>
<li><p>有些情况下，可以使用连接代替子查询。
因为使用 join，Mysql 不需要在 <strong>内存</strong> 中创建 <strong>临时表(不使用索引)</strong>，
除非指定了联接条件时，满足查询条件的记录行数少的表为[驱动表]，未指定联接条件时，行数少的表为[驱动表]，多表联合查询时</p></li>
</ol>


<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='sql'><span class='line'><span class="k">select</span> <span class="o"><em></span> <span class="k">from</span> <span class="n">dept</span><span class="p">,</span> <span class="n">emp</span> <span class="k">where</span> <span class="n">dept</span><span class="p">.</span><span class="k">no</span> <span class="o">=</span> <span class="n">emp</span><span class="p">.</span><span class="k">no</span><span class="p">;</span> <span class="o">//</span> <span class="err">简单处理方式</span>
</span><span class='line'><span class="k">select</span> <span class="o"></em></span> <span class="k">from</span> <span class="n">dept</span> <span class="k">left</span> <span class="k">join</span> <span class="n">emp</span> <span class="k">on</span> <span class="n">dept</span><span class="p">.</span><span class="k">no</span> <span class="o">=</span> <span class="n">emp</span><span class="p">.</span><span class="k">no</span><span class="p">;</span> <span class="o">//</span> <span class="err">左连接</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><br/>
<br/></p>

<p><h2 id='4'>4. 索引生成文件</h2></p>

<p><h3 id='4.1'>索引文件</h3></p>

<p>可以通过 my.ini 看到索引的目录文件，一般每一张表有三个文件：
&ndash; .frm 记录表的结构，【innodb 数据库的数据放在外层目录的 ibdata 文件；】</p>

<ul>
<li><p>.myd 表的数据</p></li>
<li><p>.myi 记录表的索引</p></li>
</ul>


<p><br/>
<br/></p>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[SEO问题解答]]></title>
    <link href="https://TsaiKoga.github.com/blog/2017/05/31/seowen-ti-jie-da/"/>
    <updated>2017-05-31T10:34:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2017/05/31/seowen-ti-jie-da</id>
    <content type="html"><![CDATA[<p>这里有一些 SEO 方面的问题和答案，是我以前看视频整理的。</p>

<h2>目录</h2>

<h3><a href="#da">1.SEO数据分析</a></h3>

<h4><a href="#da-inside">1.1站内数据分析</a></h4>

<h4><a href="#da-outside">1.2站外数据分析</a></h4>

<h4><a href="#da-user">1.3用户数据分析</a></h4>

<h3><a href="#saturate">2.收录的饱和度</a></h3>

<h4><a href="#saturate-record">2.1收录的饱和度</a></h4>

<h4><a href="#saturate-link">2.2链接的饱和度</a></h4>

<h4><a href="#score-point">2.3得分临界点</a></h4>

<h3><a href="#weight">3.SEO权重最优操作原则</a></h3>

<h4><a href="#weight-minus">3.1减法操作</a></h4>

<h5><a href="#minus-keyword">3.1.1关键词减法</a></h5>

<h5><a href="#minus-content">3.1.2内容的减法</a></h5>

<h3><a href="#title">4.网站标题最佳设置的最佳原则</a></h3>

<h4><a href="#match">4.1匹配</a></h4>

<h4><a href="#focus">4.2集中</a></h4>

<h4><a href="#diff">4.3差异</a></h4>

<h4><a href="#brand">4.4品牌</a></h4>

<br/>


<br/>




<h2 id="da">SEO数据分析</h2>


<p>有三种数据分析，分别如下：</p>

<h3 id="da-inside">站内数据分析</h3>


<hr />

<p>查看<strong>服务器日志</strong>，日志记录了所有网站行为 [什么时候，什么人，做了什么事，出现什么情况]。</p>

<p><strong>什么人为IP：</strong> 可以用站长工具查看IP来历</p>

<p><strong>出现情况：</strong>   200,404&hellip; 【200：访问成功，404：网页不存在，503：服务器暂时不可用。】
<a href="http://blog.csdn.net/j2eeweiwei/article/details/7058026">出现情况对照表</a></p>

<h4>看什么：</h4>

<p>1.查看百度蜘蛛的爬行。</p>

<p> 【蜘蛛没有爬；页面不过关】</p>

<p>  查找方式：日志中搜索baiduspider</p>

<p>2.了解网站有没有死链接</p>

<p>  查找方式：查看404状态，记住是404状态，不是404字节。</p>

<p>  解决方法：1.整理出来 2.站长提交， 3.robots屏蔽。</p>

<p>3.同一个IP对网站的访问情况。</p>

<p>4.了解网站安全状态</p>

<p>除了POST，GET，还有HEAD，而HEAD是尝试性路径，查看有没有。</p>

<br/>




<h3 id="da-outside">二、站外数据分析【链接存在的价值：好的链接被推荐在其他网站】</h3>


<hr />

<p><strong>1.通过站长工具查看外链分析，看到外链情况：</strong></p>

<p>如果一个网站的被链接网页的url都为首页，那么这些外链异常，网站很容易被降权。</p>

<p>内链比首页外链多，这个才是正常的。参与排名的大多都是内页。</p>

<p>链接你网站的url是否都是那几个地方。链接来源单一。</p>

<p>所以查看：1.被链接网页的url，2.链接你网站的url</p>

<br/>


<p><strong>2.查看收录比</strong>
收录比指的是 网站的收录数量/网站的总体数量（没有60%以上都是比较差的）。</p>

<p>如果收录比比较低，那么就不要更新了。进行站内页面的调整，尽可能让你所有站内页面都被收录。</p>

<p>页面增加附加价值。</p>

<br/>




<h3 id="da-user"> 三、用户数据分析</h3>


<hr />

<p>有PV，IP，UV，跳出率，停留时间，点击量，关注量。</p>

<p><strong>PV：</strong> 被用户浏览的数量级。</p>

<p><strong>UV/PV：</strong> 如果一个用户平均访问2个页面，那么这个网站的结构和引导做的很差。【可以通过引导使pv量上升】</p>

<p>跳出率单纯说高和低其实是不对的，如果一个网站只有一个页面，他的跳出率是100%，如果他对一个页面看了很久才关掉，也没错。</p>

<p>跳出率 + 停留时间 + 页面信息量 才能决定好坏。</p>

<br/>


<br/>




<h2 id="saturate">SEO饱和度研究</h2>




<h3 id="saturate-record">收录的饱和度：</h3>


<hr />

<p><strong>1.有时候收录200多后来变成30多，再后来变成200多，这是为什么呢？</strong></p>

<p>因为百度更新数据所造成的。</p>

<p><strong>2.为什么持续更新，某个期间网站收录一直没变化？</strong></p>

<p><strong>网站收录饱和度：</strong> 当你的网站权重值在这个期间变化不大，在站内的页面有很多；</p>

<p>给予内页权重值一定，新产生的页面获得权重值，老的页面没有权重就沉底了，被取消收录了。</p>

<p>所以，权重有突破，收录才有突破。</p>

<p>本身内页的得分来源于首页。</p>

<br/>


<br/>




<h3 id="saturate-link">链接的饱和度：</h3>


<hr />

<p>搜索引擎对于一个网站是有控制的，像股票一样有一个波动状态，防止波动太大。</p>

<p><strong>黑帽：</strong> 通过短期实现一个网站权重迅速提升，使波动非常陡。</p>

<p>黑帽的风险非常大，像外链迅速飙升。</p>

<p><strong>1.当你的网站涨幅缓慢，搜索引擎就会制定一个最高的标准线和最低标准线。</strong></p>

<p>当你的网站超过最高标准线，那么就属于异常。这样搜索引擎就会进行考核或是被K。</p>

<p>所以要控制链接，不要让其增长过快。</p>

<p><strong>2.如何控制数量？</strong></p>

<p>  1.友情链接</p>

<p>  曾经有个做seo的论坛叫狼雨seo，刚出现就在百度第一位，原来他有300多个友情链接，并且以滚动方式运行。</p>

<p>  一般控制在30-40个就足够了，超过了就被干掉。</p>

<p>  2.一般性外链</p>

<p>  一天控制增长在50个之内，一般用站外的文章区发外链，不要发站内文章；发的链接不要指向首页。</p>

<p>  链接的价值：传播。像把链接改为背景颜色看不出的，这种行为搜索引擎看做作弊。</p>

<p>  3.自然链接</p>

<p>  就是发布文章底部分享链接，而不是在文章的中间加个关键字，就把他做成链接。</p>

<p>  不要拿自己的网站内容发链接，而是拿别人网站东西发，这是为了防止同质化问题。</p>

<p>  <br/>
  <br/></p>

<h3 id="score-point">得分临界点：</h3>


<hr />

<p>不管是收录标，排名准或是外链是否要计算，都需要转变为数值。通过数值对比来判断是否收录。</p>

<p>例如：你的内容搜索引擎给的分数是200，通过计算你得分是198，那么你不会被收录。</p>

<p>198和200相差2分，当你的一个友情链接降权了，被扣分了。</p>

<br/>


<br/>




<h2 id="weight">SEO权重最优操作原则</h2>




<h3 id="weight-minus">减法操作：</h3>


<hr />

<h4 id="minus-keyword">1.关键词减法：</h4>


<p>网站权重是有限的，如果让其参与的关键词过多，导致每个关键词获得的得分值很低。</p>

<p><em>例子：如果你有200分，“装B表情”给100分，“在线表情制作”给80分，“装B表情网”就20分，不够收录标准。</em></p>

<p>所以权重高，排名靠前。关键词会分享分数，而分数是要参与排名的。</p>

<p><em>建议： 3-4个主关键词，1个品牌词。 其他词放到内页去。</em></p>

<p>企业网站内页的长尾词40-50个。门户网站，商店之类的B2B网站内页长尾词能做多少就多少，因为他们需要的是推广。</p>

<br/>




<h4 id="minus-content">2.内容的减法：</h4>


<p>1）<strong>站内主题数：</strong> 用户主题数的关联性不高（一个网站有一个服务，又有另一个服务），所以关联性强的单独一个网站。</p>

<p>2）<strong>站内页面数：</strong> 有些站长每天发帖子，导致网站臃肿；要看所发的帖子是否“受众”。</p>

<p>如果发的页面从来没被人浏览，搜索引擎认为是低质量页面。网站页面数越多，被用户浏览到几率越低。</p>

<p>企业网站收录需100左右，所以整个网站页面数就150-200左右，不要过多。</p>

<p>对于细分类的商城可以定主题，如果是综合性的商城，只能打品牌，没法参与关键词排名。</p>

<p>3）<strong>站内信息数：</strong> 一个页面内的信息数量，（像header和footer的文字属于样板文字）单个页面样板文字减少，</p>

<p>因为如果你的样板文字占太大（像友情链接出现在首页就行了）。</p>

<p>页面样板文字30%；内容70%。图片说明+视频说明+评论，更好的降低样板文字的比例。</p>

<br/>


<br/>




<h2 id="title">网站标题最佳设置的最佳原则</h2>


<hr />

<p>标题是搜索引擎排名的最重要元素之一。</p>

<h3 id="match">1.匹配</h3>


<p><strong>字符匹配：</strong> 用户的查询词与你标题上字符的匹配程度【完全匹配，全部匹配(对查询词进行拆分也叫分词)，部分匹配】。</p>

<p>这几种匹配都参与排名，但是优先级不同。完全匹配 > 全部匹配 > 部分匹配</p>

<p><strong>需求匹配：</strong> 需求有很多，所以要判断大小，需求大的会位于前面。</p>

<p>可以通过百度输入部分值查看需求最大的标题，然后标题要突显这个需求大的标题。</p>

<br/>




<h3 id="focus">2.集中（直接影响排名）</h3>


<p>先做一些词的排名，带来流量后，再使用其他词。（一般建议3-4个关键词）</p>

<p>3个关键+1品牌词，如：在线表情制作-表情下载-二维码表情制作-装B表情【最后一个是品牌词】</p>

<p>栏目页：www.zhuangbbq.com/emotions +1个品牌词,如：表情列表-装B表情</p>

<br/>




<h3 id="diff">3.差异（间接影响排名）：跟别人不一样，突出。</h3>


<p>注意：单击会影响排名，差异性直接影响点击</p>

<p>宿舍和在线宿舍，在线宿舍较突出，并且在线可能有吸引力，差异是为了点击，没有点击就没用。</p>

<p>看似差异和匹配矛盾，其实不然；差异是间接的影响，可以在早期没流量时做。</p>

<br/>




<h3 id="brand">4.品牌</h3>


<p>如果百度上搜索到的名字出现它的ico，证明它是高权重网站。</p>

<p>其实是由搜索品牌词决定的。建议XXX有限公司缩为4个字。</p>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[CSS知识总结]]></title>
    <link href="https://TsaiKoga.github.com/blog/2017/04/09/csszhi-shi-zong-jie/"/>
    <updated>2017-04-09T10:27:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2017/04/09/csszhi-shi-zong-jie</id>
    <content type="html"><![CDATA[<h3>XHTML必要规则：</h3>

<hr />

<ol>
<li>标签都要小写</li>
<li>属性名要小写</li>
<li>严格的嵌套（例如：<code>&lt;i&gt;&lt;b&gt;Hello&lt;/b&gt;&lt;/i&gt; &lt;!--&gt;而不是&lt;b&gt;&lt;i&gt;hello&lt;/i&gt;&lt;/b&gt;&lt;--&gt;</code>）</li>
<li>标签必须封闭</li>
<li>空元素标记也要封闭（例如：<code>&lt;img/&gt;&lt;br/&gt;</code>）</li>
<li>属性要用双引号</li>
<li>属性使用完整形式（例如：<code>&lt;button disabled=true&gt;&lt;/button&gt;&lt;!--&gt;而不是直接disabled&lt;--&gt;</code>）</li>
<li>结构标记不能放在内容标记中（如<code>&lt;table&gt;不能放在&lt;p&gt;中</code>）</li>
</ol>


<br/>


<br/>


<h2>CSS 总结</h2>

<hr />

<h3>引入CSS</h3>

<hr />

<ul>
<li>行内式：通过<code>&lt;style type="text/css"&gt;&lt;/style&gt;</code>直接引入</li>
<li>嵌入式：通过<code>&lt;head&gt;</code>中引入</li>
<li>链接式：通过<code>&lt;link href=“style/style.css" rel="stylesheeet" type="txet/css"/&gt;</code>引入</li>
<li>导入式：通过<code>&lt;style type="text/css"&gt;@import "style.css";&lt;/style&gt;</code>，注意：导入式是等到加载完后才导入css的，所以会有一瞬间没有css样式</li>
</ul>


<br/>


<h3>选择器</h3>

<hr />

<ul>
<li>标记选择器：例如p、h1、 h2等标签去掉尖括号</li>
<li>类别选择器：.class</li>
<li>ID选择器： #id</li>
<li>复合选择器：</li>
<li>交集选择器：将两个选择器并列在一起，如h1.spec</li>
<li>并集选择器：通过逗号分隔开，如h1, h2</li>
<li>后代选择器：通过空格分隔，这里的后代可以是儿子，孙子等</li>
<li>子选择器：通过>号分隔，与后代不同，它只适用于儿子。</li>
</ul>


<p>优先级：行内样式 > ID样式 > 类别样式 > 标记样式</p>

<br/>


<h3>盒子模型</h3>

<hr />

<p>margin &ndash; border -padding &ndash; content</p>

<br/>


<p>由于盒子模型的 border 和 padding，实际设置宽度应该减去这两个值，才能保证盒子的宽度不会变大；
还好 CSS3 引入box-sizing: border-box，这个属性可以让 padding 和 border 不对 width 造成影响。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
</pre></td><td class='code'><pre><code class='css'><span class='line'><span class="nc">.fancy</span> <span class="p">{</span>
</span><span class='line'>  <span class="k">width</span><span class="o">:</span> <span class="m">500px</span><span class="p">;</span>
</span><span class='line'>  <span class="k">margin</span><span class="o">:</span> <span class="m">20px</span> <span class="k">auto</span><span class="p">;</span>
</span><span class='line'>  <span class="k">padding</span><span class="o">:</span> <span class="m">50px</span><span class="p">;</span>
</span><span class='line'>  <span class="k">border</span><span class="o">:</span> <span class="k">solid</span> <span class="nb">blue</span> <span class="m">10px</span><span class="p">;</span>
</span><span class='line'>  <span class="o">-</span><span class="n">webkit</span><span class="o">-</span><span class="n">box</span><span class="o">-</span><span class="n">sizing</span><span class="o">:</span> <span class="k">border</span><span class="o">-</span><span class="n">box</span><span class="p">;</span>
</span><span class='line'>     <span class="o">-</span><span class="n">moz</span><span class="o">-</span><span class="n">box</span><span class="o">-</span><span class="n">sizing</span><span class="o">:</span> <span class="k">border</span><span class="o">-</span><span class="n">box</span><span class="p">;</span>
</span><span class='line'>          <span class="n">box</span><span class="o">-</span><span class="n">sizing</span><span class="o">:</span> <span class="k">border</span><span class="o">-</span><span class="n">box</span><span class="p">;</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<br/>


<h3>布局Postion</h3>

<hr />

<p>提到 postion，必须知道一件事，就是元素是否会被 postioned，因为 absolute 需要他来调整位置。
目前只有一个属性值 static 不会被positioned，其他都会。</p>

<br/>


<ul>
<li>static: 默认的 position 值，不会被positioned。</li>
<li>relative: 通过 top / right / bottom / left 偏离原位置，<strong>其他元素位置不会受到它偏离后的影响</strong></li>
<li>fixed: 固定定位，脱离文档流；手机版本不支持，详情请看<a href="http://bradfrost.com/blog/mobile/fixed-position/">解决方法</a></li>
<li>absolute: 对于最近的 <strong>positioned 祖先</strong> 绝对定位，像fixed一样通过 top / right / bottom  /left 来调整位置</li>
</ul>


<br/>


<h3>浮动</h3>

<hr />

<p>浮动主要是float,有left，right。他会对相邻元素造成影响。通过clear属性可以清除影响，如：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
</pre></td><td class='code'><pre><code class='css'><span class='line'><span class="nc">.box</span> <span class="p">{</span>
</span><span class='line'>  <span class="k">float</span><span class="o">:</span> <span class="k">left</span><span class="p">;</span>
</span><span class='line'>  <span class="k">width</span><span class="o">:</span> <span class="m">200px</span><span class="p">;</span>
</span><span class='line'>  <span class="k">height</span><span class="o">:</span> <span class="m">100px</span><span class="p">;</span>
</span><span class='line'>  <span class="k">margin</span><span class="o">:</span> <span class="m">1em</span><span class="p">;</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'><span class="nc">.after-box</span> <span class="p">{</span>
</span><span class='line'>  <span class="k">clear</span><span class="o">:</span> <span class="k">left</span><span class="p">;</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>如果 div 中元素（例如图片）设置了浮动，div 反而比他里面这个元素（图片）小，该怎么办？
通过设置为 <code>overflow: auto</code> 解决，IE6还要设置<code>zoom: 1</code></p>

<br/>


<br/>


<h3>响应式布局：</h3>

<hr />

<h4>设置 Meta 标签：</h4>

<hr />

<p>大多数移动浏览器将HTML页面放大为宽的视图（viewport）以符合屏幕分辨率。你可以使用视图的meta标签来进行重置。下面的视图标签告诉浏览器，使用设备的宽度作为视图宽度并禁止初始的缩放。在<head>标签里加入这个meta标签。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='css'><span class='line'><span class="o">&lt;</span><span class="nt">meta</span> <span class="nt">name</span><span class="o">=</span><span class="s2">&quot;viewport&quot;</span> <span class="nt">content</span><span class="o">=</span><span class="s2">&quot;width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no&quot;</span><span class="o">&gt;</span>
</span></code></pre></td></tr></table></div></figure>


<p>viewport是网页默认的宽度和高度，上面这行代码的意思是，网页宽度默认等于屏幕宽度（width=device-width），原始缩放比例（initial-scale=1）为1.0，即网页初始大小占屏幕面积的100%。
<strong> 注意：（user-scalable = no 属性能够解决 iPad 切换横屏之后触摸才能回到具体尺寸的问题。 ）</strong></p>

<br/>


<h4>通过媒介查询来设置样式 Media Queries：</h4>

<hr />

<p>Media Queries 是响应式设计的核心。
它根据条件告诉浏览器如何为指定视图宽度渲染页面。假如一个终端的分辨率小于 980px，那么可以这样写：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='css'><span class='line'><span class="k">@media</span> <span class="nt">screen</span> <span class="nt">and</span> <span class="o">(</span><span class="nt">max-width</span><span class="o">:</span> <span class="nt">980px</span><span class="o">)</span> <span class="p">{</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<br/>


<h4>设置多种视图宽度</h4>

<hr />

<p>假如我们要设定兼容 iPad 和 iphone 的视图，那么可以这样设置：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='css'><span class='line'><span class="c">/** iPad **/</span>
</span><span class='line'><span class="k">@media</span> <span class="nt">only</span> <span class="nt">screen</span> <span class="nt">and</span> <span class="o">(</span><span class="nt">min-width</span><span class="o">:</span> <span class="nt">768px</span><span class="o">)</span> <span class="nt">and</span> <span class="o">(</span><span class="nt">max-width</span><span class="o">:</span> <span class="nt">1024px</span><span class="o">)</span> <span class="p">{}</span>
</span><span class='line'><span class="c">/** iPhone **/</span>
</span><span class='line'><span class="k">@media</span> <span class="nt">only</span> <span class="nt">screen</span> <span class="nt">and</span> <span class="o">(</span><span class="nt">min-width</span><span class="o">:</span> <span class="nt">320px</span><span class="o">)</span> <span class="nt">and</span> <span class="o">(</span><span class="nt">max-width</span><span class="o">:</span> <span class="nt">767px</span><span class="o">)</span> <span class="p">{}</span>
</span></code></pre></td></tr></table></div></figure>


<br/>


<h4>图片文字也要响应式</h4>

<hr />

<p>1.宽度需要使用百分比</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='css'><span class='line'><span class="nf">#head</span> <span class="p">{</span> <span class="k">width</span><span class="o">:</span> <span class="m">100</span><span class="o">%</span> <span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<br/>


<p>2.处理图片缩放的方法
简单的解决方法可以使用百分比，但这样不友好，会放大或者缩小图片。那么可以尝试给图片指定的最大宽度为百分比。假如图片超过了，就缩小。假如图片小了，就原尺寸输出。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='css'><span class='line'><span class="nt">img</span> <span class="p">{</span> <span class="k">width</span><span class="o">:</span> <span class="k">auto</span><span class="p">;</span> <span class="k">max-width</span><span class="o">:</span> <span class="m">100</span><span class="o">%</span><span class="p">;</span> <span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<br/>


<p>3.相对大小的文字：
字体也不能使用绝对大小（px），而只能使用相对大小（em）。
先指定全局字体，这里设置为页面默认大小的100%，即16像素：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='css'><span class='line'><span class="nt">body</span> <span class="p">{</span>
</span><span class='line'><span class="err">　</span><span class="k">font</span><span class="o">:</span> <span class="k">normal</span> <span class="m">100</span><span class="o">%</span> <span class="n">Helvetica</span><span class="o">,</span> <span class="n">Arial</span><span class="o">,</span> <span class="k">sans-serif</span><span class="p">;</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>然后</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='css'><span class='line'><span class="nt">h1</span> <span class="p">{</span>
</span><span class='line'><span class="err">　</span><span class="k">font-size</span><span class="o">:</span> <span class="m">1.5em</span><span class="p">;</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>h1的大小是默认大小的1.5倍，即24像素（24/16=1.5）。</p>

<br/>


<h5>vw 和 vh</h5>

<p>vw 和 vh 是相对视区宽度和高度，这里的 视区 指的是网页宽度高度，也就是 window.innerWidth 和 window.innerHeight
然后 vw 如果为 10 ，也就是该元素相对网页宽度是 1/10；</p>

<p>相关响应式资料资料：<a href="http://www.ruanyifeng.com/blog/2012/05/responsive_web_design.html">http://www.ruanyifeng.com/blog/2012/05/responsive_web_design.html</a></p>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[JQuery重要知识点]]></title>
    <link href="https://TsaiKoga.github.com/blog/2017/03/10/jqueryzhong-yao-zhi-shi-dian/"/>
    <updated>2017-03-10T15:14:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2017/03/10/jqueryzhong-yao-zhi-shi-dian</id>
    <content type="html"><![CDATA[<p>对于Jquery，用起来很像很简单；但是有些知识点经常会忘记。这里特别写一篇来巩固。</p>

<h3>加载：</h3>

<h4>关于 ready 和 onLoad 的区别</h4>

<p>两个不同点：</p>

<p>1)
只有文档完全下载到本地，才会触发<code>window.onload</code>事件，这意味着所有事件对于Javascript都是可以操作的。</p>

<p>通过<code>$(document).ready()</code>注册的事件处理程序，则会在 <strong>DOM</strong> 完全就绪并可以使用时调用。这意味着
所有元素对于脚本都是可以访问的。但不意味所有关联文件（例如DOM的图片）都已下载完毕。</p>

<p>换句话说：当HTML都下载完成别解析成为DOM树后，代码才可以运行。</p>

<br/>


<p>2)
对于<code>onload</code>属性一次只能保存一个函数引用，所以不能再现有行为上添加新的行为。</p>

<p>对于<code>$(document).ready()</code>调用这方法每次都会向内部的行为队列添加新函数。当页面加载完成后，所有函数会被执行。按照注册他们的顺序依次执行。</p>

<br/>


<p>关于<code>$(document).ready()</code>结构，实际上是在基于<code>document</code>这个DOM元素构建成的JQuery对象上调用<code>ready()</code>方法。</p>

<p>实际上可写成：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="nx">$</span><span class="p">(</span><span class="nb">document</span><span class="p">).</span><span class="nx">ready</span><span class="p">({</span>
</span><span class='line'>  <span class="p">...</span> <span class="p">...</span>
</span><span class='line'><span class="p">});</span>
</span></code></pre></td></tr></table></div></figure>


<p>或写成：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="nx">$</span><span class="p">(</span><span class="kd">function</span><span class="p">(){</span>
</span><span class='line'>  <span class="p">...</span>
</span><span class='line'><span class="p">});</span>
</span></code></pre></td></tr></table></div></figure>




<br/>


<hr />

<h3>事件：</h3>

<h4>事件捕获</h4>

<p>允许多个元素响应单击事件的策略</p>

<h4>事件冒泡</h4>

<p>当事件发生时，会首先发送给最具体的元素，在这个元素获得响应机会后，事件会 <strong>向上冒泡到更一般</strong> 的元素。</p>

<br/>


<p><strong>如何解决事件冒泡副作用</strong></p>

<p>访问事件对象e</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="kd">function</span><span class="p">(</span><span class="nx">e</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>  <span class="k">if</span> <span class="p">(</span><span class="nx">e</span><span class="p">.</span><span class="nx">target</span> <span class="o">==</span> <span class="k">this</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>    <span class="p">...</span> <span class="p">...</span>
</span><span class='line'>  <span class="p">}</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>关于<code>event.stopPropagation()</code>阻止所有DOM响应这个事件，但是不能阻止默认操作;
必须要用<code>event.preventDefault()</code>来在操作前终止事件。</p>

<br/>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="nx">$</span><span class="p">(</span><span class="s1">&#39;switch&#39;</span><span class="p">).</span><span class="nx">on</span><span class="p">(</span><span class="s1">&#39;click&#39;</span><span class="p">,</span> <span class="s1">&#39;button&#39;</span><span class="p">,</span> <span class="kd">function</span><span class="p">(){</span> <span class="p">})</span>
</span></code></pre></td></tr></table></div></figure>


<p>相当于</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="nx">$</span><span class="p">(</span><span class="s1">&#39;switch&#39;</span><span class="p">).</span><span class="nx">on</span><span class="p">(</span><span class="s1">&#39;click&#39;</span><span class="p">,</span> <span class="kd">function</span><span class="p">(</span><span class="nx">e</span><span class="p">){</span>
</span><span class='line'>  <span class="k">if</span><span class="p">(</span><span class="nx">e</span><span class="p">.</span><span class="nx">target</span> <span class="o">==</span> <span class="s1">&#39;button&#39;</span><span class="p">){</span> <span class="p">}</span>
</span><span class='line'><span class="p">})</span>
</span></code></pre></td></tr></table></div></figure>


<p>模仿用户操作行为的方法 <code>trigger()</code> 它提供了和<code>on()</code>方法一样的简写方法。
像<code>click()</code>等on动作不带参数会自动触发。</p>

<br/>


<hr />

<h3>属性值：</h3>

<h4>值回调</h4>

<p>把回调函数作为参数传递</p>

<h4>HTML 属性和 DOM 属性的区别</h4>

<p><strong>HTML属性值:</strong> 页面标记中放在引号的值</p>

<p><strong>DOM属性值:</strong> Javascript能存取的值，可以通过chrome的elements检查器查看properties</p>

<p><strong>不同点：</strong> 有些DOM名称和HTML不同，例如：className;
有些DOM属性HTML是没有的，DOM的<code>attr()</code>就没发操作他们。</p>

<p>测试DOM属性而非HTML属性才可确保跨浏览器的一致性。如：<code>prop()</code>来获取DOM属性值，而非<code>attr()</code></p>

<p>最大不同在操作表单值：DOM和HTML操作表单的名称很多不同，最好不用<code>prop()</code>和<code>attr()</code>，而用<code>val()</code></p>

<hr />

<h3>Ajax</h3>

<h4>单向数据传输：</h4>

<p>AHAH(async http and html)用load()</p>

<p>服务器返回的JSON是字符串，需要变成JS字面量；</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="nx">$</span><span class="p">.</span><span class="nx">getJSON</span><span class="p">(</span><span class="s1">&#39;.json&#39;</span><span class="p">,</span> <span class="kd">function</span><span class="p">(</span><span class="nx">data</span><span class="p">){</span>
</span><span class='line'>  <span class="p">...</span>
</span><span class='line'><span class="p">});</span>
</span></code></pre></td></tr></table></div></figure>


<p><strong>向页面注入脚本：</strong></p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="nx">$</span><span class="p">.</span><span class="nx">getScript</span><span class="p">()</span>
</span></code></pre></td></tr></table></div></figure>


<p><strong>获取XML：</strong></p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="nx">$</span><span class="p">.</span><span class="nx">get</span><span class="p">(</span><span class="s1">&#39;.xml&#39;</span><span class="p">,</span> <span class="kd">function</span><span class="p">(</span><span class="nx">data</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>    <span class="p">...</span>
</span><span class='line'><span class="p">})</span>
</span></code></pre></td></tr></table></div></figure>


<h4>双向数据传递：</h4>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="nx">get</span><span class="p">(</span><span class="s1">&#39;a.php&#39;</span><span class="p">,</span> <span class="nx">args</span><span class="p">,</span> <span class="kd">function</span><span class="p">(){})</span>
</span></code></pre></td></tr></table></div></figure>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="nx">post</span><span class="p">(</span><span class="s1">&#39;a.php&#39;</span><span class="p">,</span> <span class="nx">args</span><span class="p">,</span> <span class="kd">function</span><span class="p">(){})</span>
</span></code></pre></td></tr></table></div></figure>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="nx">load</span><span class="p">(</span><span class="s1">&#39;a.php&#39;</span><span class="p">,</span> <span class="nx">args</span><span class="p">,</span> <span class="kd">function</span><span class="p">(){})</span>
</span></code></pre></td></tr></table></div></figure>


<p>load在包含数据对象参数时，会使用post方法</p>

<p>ajaxStart()回调，ajax请求开始且尚未进行任何其他传输时 和 read() 一样只能由$(document)调用</p>

<p>ajaxStop()回调，ajax最后一次请求结束时调用，和 read() 一样只能由$(document)调用</p>

<p>ajaxError()回调，参数是一个XMLHttpRequest的引用。</p>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[React Node 初尝试]]></title>
    <link href="https://TsaiKoga.github.com/blog/2016/12/20/React-Node-chu-chang-shi/"/>
    <updated>2016-12-20T20:29:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2016/12/20/React-Node-chu-chang-shi</id>
    <content type="html"><![CDATA[<p>这是第一次写React和Node，选用的是前端Material-ui框架，后端使用的是Express框架，数据库采用的是Mongodb。</p>

<p>项目代码在：<a href="https://github.com/TsaiKoga/lilu_movie">GitHub/lilu_movie</a></p>

<p>这是一个通过从电影天堂抓取数据并显示的电影网站，demo部署在heroku上面。</p>

<h2>安装</h2>

<hr />

<p>首先安装express框架；</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>npm install express --save
</span></code></pre></td></tr></table></div></figure>


<p>生成文件后，可以通过 npm start 启动应用。</p>

<p>注意：ejs 从3.x后不支持layout，可以通过express-partials ，但是不支持4，4之后用include</p>

<p>紧接着我迫不及待安装material-ui：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>npm install material-ui --save
</span></code></pre></td></tr></table></div></figure>


<p>然后出现错误：</p>

<p><img src="https://TsaiKoga.github.com/images/posts/2016-12-20/material-ui-error.png" alt="material-ui-error" /></p>

<p>所以必须安装react依赖：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>npm install react@^15.0.0 --save
</span><span class='line'>
</span><span class='line'>npm install react-dom@^15.0.0 --save
</span><span class='line'>
</span><span class='line'>npm install react-tap-event-plugin@^1.0.0 --save
</span></code></pre></td></tr></table></div></figure>


<p>安装nodemon</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>nodemon ./bin/www <span class="c">#更改会自动重启服务</span>
</span></code></pre></td></tr></table></div></figure>


<p>本地安装数据库mongodb</p>

<p>然后npm安装操作mongodb的mongoose</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>npm install mongoose
</span><span class='line'>
</span><span class='line'>npm install express-mongoose
</span></code></pre></td></tr></table></div></figure>


<p>接着你会发现按照material-ui的import引入报错，</p>

<p>使用es6查看系统支持哪些es6语法</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>npm install es6-checker
</span></code></pre></td></tr></table></div></figure>


<p>因为react使用es6和jsx语法，所以需要转化，安装如下包：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>npm install babel-loader babel-core babel-preset-es2015 —save-dev
</span><span class='line'>
</span><span class='line'>npm install jsx-loader —save-dev
</span><span class='line'>
</span><span class='line'>npm install babel-preset-react
</span></code></pre></td></tr></table></div></figure>


<p>安装webpack</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>npm install webpack —save-dev
</span><span class='line'>
</span><span class='line'>
</span><span class='line'>npm install css-loader —save-dev
</span><span class='line'>
</span><span class='line'>
</span><span class='line'>npm install webpack-dev-server —save-dev  <span class="c"># 前端文件更新就能自动热启动，会启动端口，默认8080</span>
</span></code></pre></td></tr></table></div></figure>


<p>这里有必要提一下：-save-dev代表安装的包适用于开发的，类似于rails中安装Gem放在:development环境下，这样生产环境就不会安装</p>

<p>然后在webpack配置文件中babels的loaders中query加入presets</p>

<p>因为需要一些css文件，react通过require style文件(js 文件中直接require css 文件)，需要安装</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>npm install style-loader —save-dev
</span><span class='line'>
</span><span class='line'>npm install css-loader —save-dev // 这个和style一起用才有效果
</span></code></pre></td></tr></table></div></figure>


<p>在webpack中的config 加上loader: &ldquo;style-loader!css-loader”，就不用require使用style!css!了</p>

<br/>


<h2>启动脚本：</h2>

<hr />

<p>配置package.json文件，给script添加命令</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='js'><span class='line'> <span class="s2">&quot;start&quot;</span><span class="o">:</span> <span class="p">[</span><span class="s2">&quot;node ./bin/www&quot;</span><span class="p">,</span> <span class="s2">&quot;webpack&quot;</span><span class="p">],</span>
</span></code></pre></td></tr></table></div></figure>


<p>编写webpack.config.js配置文件，更改html引入文件</p>

<p>在webpack-dev-server 没有真正生成文件，还得要引入<script src=“localhost:8080/assets/bundle.js"></script></p>

<p>运行</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>npm run dev
</span></code></pre></td></tr></table></div></figure>


<p>看webpack-dev-server效果</p>

<br/>


<h2>Express后端流程改变：</h2>

<hr />

<p>刚开始，我用一贯的后台思路通过routes渲染页面，页面html引入react的js文件，reactjs文件link后台js响应；后台相应通过连接mongodb获取数据库内容。</p>

<p>很成功，获取到相应的内容了，但是因为使用react(React适合做SPA)，所以不好每次都取加载一次内容，所以就不用引擎模板，这些数据如何放入state让react用diff算法自己计算呢？怎样变成单页面应用呢？</p>

<p>这时候我想到就是ajax；上网google一下，发现用fetch能实现像ajax那样的请求。同一个component可以很容易实现fetch数据改变this的state。</p>

<p>详情更改请看我的这个commit：<a href="https://github.com/TsaiKoga/lilu_movie/commit/16fef9918a0fc1a2a34e851d88328fcd99b1c2c8">add client store to fetch movie&rsquo;s data from server</a></p>

<p>这时候发现不知道怎么通过点击侧边栏标签，渲染新页面（注意：侧边栏是一个组件，而右边的电影列表又是一个组件，他们是两个不同的组件）</p>

<p><img src="https://TsaiKoga.github.com/images/posts/2016-12-20/sidebar.png" alt="侧边栏组件" /></p>

<br/>


<h2>使用React-Router</h2>

<hr />

<p>由于react规定父元素只能改变子元素，但是不好将子元素改变父元素；</p>

<p>一般我们都会把许多内容都搞到最顶级那个父元素的state，这样其他都有可能与他有关联，而子元素改变父元素的state的方法就是通过回调setState；</p>

<p>所以这里我们可以将movies放在最顶的component，然后点击标签，就去回调去改变这个父元素的state，用到这个state的子元素就会刷新。</p>

<p>例如：父组件有一个属性callbackParent=某个callback函数。然后 子组件 通过事件 触发this.props.callbackParent这个函数，把你要的值传给callback，callback立马设置给父组件state</p>

<p> 方案：<a href="http://stackoverflow.com/questions/22639534/pass-props-to-parent-component-in-react-js">stackoverflow</a></p>

<p> 代码详见这个 <a href="https://github.com/TsaiKoga/lilu_movie/commit/248258b5faf0161f66655c745c2bc8e33ffc9798">commit</a></p>

<p><strong>但是这样太hacky了，违背react理念，代码难理解；</strong></p>

<br/>


<p>有没有其他更好的办法呢？</p>

<p>Google查找答案发现有两种方法：</p>

<ol>
<li><p>使用react-router</p></li>
<li><p>如果不是用react-router，则得这样写<a href="https://github.com/ReactTraining/react-router/blob/master/docs/Introduction.md">https://github.com/ReactTraining/react-router/blob/master/docs/Introduction.md</a></p></li>
</ol>


<p>react-route根据history传入的链接，找到你对应routes的component，然后改变children，成功渲染改组件。</p>

<br/>


<br/>


<p>对于不同组件改变同个内容还是使用react-router</p>

<br/>


<br/>


<p>使用react-router发现client端通过router的链接，局部更新内容；</p>

<p>这样子说，完全不需要server后台每个路由每次渲染不同页面了，只需要server不同链接给出不同内容，然后渲染同一个页面，这个页面通过react-router去改变内容即可。</p>

<p>所以删除后端所有router路由；</p>

<p>按照React Router官方教程实现相应代码。</p>

<br/>


<br/>


<p>这时候发现一个问题：</p>

<p>渲染同一个页面就要在后端引入前端的routes，也就需要到es6了，但是之前后端没有通过webpack进行es6的转化，所以还要对后端的入口文件进行webpack转化。</p>

<br/>


<br/>


<p>对后端server.js进行webpack的bundle后，很容易报错，首先要在web pack中排除掉node_module的文件，然后需要引入各种loader；</p>

<br/>


<p>server端要import client端的routes过来，但是route的component会引用相应的component。如果遇到client的内容，有些react-router/server是处理不了的，会报没有window错误。</p>

<br/>


<p>以下是最终的webpack.server.config.js</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
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<span class='line-number'>41</span>
<span class='line-number'>42</span>
<span class='line-number'>43</span>
</pre></td><td class='code'><pre><code class='js'><span class='line'><span class="kd">var</span> <span class="nx">webpack</span> <span class="o">=</span> <span class="nx">require</span><span class="p">(</span><span class="s2">&quot;webpack&quot;</span><span class="p">);</span>
</span><span class='line'><span class="kd">var</span> <span class="nx">fs</span> <span class="o">=</span> <span class="nx">require</span><span class="p">(</span><span class="s2">&quot;fs&quot;</span><span class="p">);</span>
</span><span class='line'><span class="kd">var</span> <span class="nx">path</span> <span class="o">=</span> <span class="nx">require</span><span class="p">(</span><span class="s2">&quot;path&quot;</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'><span class="nx">module</span><span class="p">.</span><span class="nx">exports</span> <span class="o">=</span> <span class="p">{</span>
</span><span class='line'>  <span class="nx">entry</span><span class="o">:</span> <span class="p">[</span>
</span><span class='line'>    <span class="nx">path</span><span class="p">.</span><span class="nx">resolve</span><span class="p">(</span><span class="nx">__dirname</span><span class="p">,</span> <span class="s1">&#39;server.js&#39;</span><span class="p">)</span>
</span><span class='line'>  <span class="p">],</span>
</span><span class='line'>
</span><span class='line'>  <span class="nx">output</span><span class="o">:</span> <span class="p">{</span>
</span><span class='line'>    <span class="nx">filename</span><span class="o">:</span> <span class="s1">&#39;server.bundle.js&#39;</span>
</span><span class='line'>  <span class="p">},</span>
</span><span class='line'>  <span class="nx">target</span><span class="o">:</span> <span class="s1">&#39;node&#39;</span><span class="p">,</span>
</span><span class='line'>
</span><span class='line'>  <span class="nx">externals</span><span class="o">:</span> <span class="nx">fs</span><span class="p">.</span><span class="nx">readdirSync</span><span class="p">(</span><span class="nx">path</span><span class="p">.</span><span class="nx">resolve</span><span class="p">(</span><span class="nx">__dirname</span><span class="p">,</span> <span class="s1">&#39;node_modules&#39;</span><span class="p">)).</span><span class="nx">concat</span><span class="p">([</span>
</span><span class='line'>    <span class="s1">&#39;react-dom/server&#39;</span><span class="p">,</span> <span class="s1">&#39;react/addons&#39;</span><span class="p">,</span>
</span><span class='line'>  <span class="p">]).</span><span class="nx">reduce</span><span class="p">(</span><span class="kd">function</span> <span class="p">(</span><span class="nx">ext</span><span class="p">,</span> <span class="nx">mod</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>    <span class="nx">ext</span><span class="p">[</span><span class="nx">mod</span><span class="p">]</span> <span class="o">=</span> <span class="s1">&#39;commonjs &#39;</span> <span class="o">+</span> <span class="nx">mod</span>
</span><span class='line'>    <span class="k">return</span> <span class="nx">ext</span>
</span><span class='line'>  <span class="p">},</span> <span class="p">{}),</span>
</span><span class='line'>
</span><span class='line'>  <span class="nx">node</span><span class="o">:</span> <span class="p">{</span>
</span><span class='line'>    <span class="nx">__filename</span><span class="o">:</span> <span class="kc">true</span><span class="p">,</span>
</span><span class='line'>    <span class="nx">__dirname</span><span class="o">:</span> <span class="kc">true</span>
</span><span class='line'>  <span class="p">},</span>
</span><span class='line'>  <span class="nx">module</span><span class="o">:</span> <span class="p">{</span>
</span><span class='line'>    <span class="nx">loaders</span><span class="o">:</span> <span class="p">[</span>
</span><span class='line'>      <span class="p">{</span>
</span><span class='line'>        <span class="nx">test</span><span class="o">:</span> <span class="sr">/\.css$/</span><span class="p">,</span>
</span><span class='line'>        <span class="nx">loader</span><span class="o">:</span> <span class="s2">&quot;style-loader!css-loader&quot;</span>
</span><span class='line'>      <span class="p">},</span> <span class="p">{</span>
</span><span class='line'>        <span class="nx">test</span><span class="o">:</span> <span class="sr">/\.js$/</span><span class="p">,</span>
</span><span class='line'>        <span class="nx">exclude</span><span class="o">:</span> <span class="sr">/node_modules/</span><span class="p">,</span>
</span><span class='line'>        <span class="nx">loader</span><span class="o">:</span> <span class="s2">&quot;babel&quot;</span><span class="p">,</span>
</span><span class='line'>        <span class="nx">query</span><span class="o">:</span> <span class="p">{</span> <span class="nx">presets</span><span class="o">:</span> <span class="p">[</span><span class="s1">&#39;react&#39;</span><span class="p">,</span> <span class="s1">&#39;es2015&#39;</span><span class="p">]</span> <span class="p">}</span>
</span><span class='line'>      <span class="p">},</span> <span class="p">{</span>
</span><span class='line'>        <span class="nx">test</span><span class="o">:</span> <span class="sr">/.json$/</span><span class="p">,</span> <span class="nx">loader</span><span class="o">:</span> <span class="s1">&#39;json-loader&#39;</span>
</span><span class='line'>      <span class="p">},</span> <span class="p">{</span>
</span><span class='line'>        <span class="nx">test</span><span class="o">:</span> <span class="sr">/.node$/</span><span class="p">,</span> <span class="nx">loader</span><span class="o">:</span> <span class="s1">&#39;node-loader&#39;</span>
</span><span class='line'>      <span class="p">}]</span>
</span><span class='line'>
</span><span class='line'>  <span class="p">}</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>事实上使用react react-router已经足够完成功能，但是考虑到如果之后想要扩展，例如现在我又要增加用户注册，登录页面；那么很有可能随着页面组件增多，这个项目将会变成意大利面；</p>

<br/>


<h2>使用Redux</h2>

<hr />

<p>页面逐渐增多，涉及到了不相关或者层级比较多的组件之间的通信；</p>

<p>以上父子组件通信已经不能满足需求，可以使用 Redux；</p>

<p>他是 <strong>观察者模式</strong>，使用 <strong>订阅分发</strong> 实现：</p>

<p>引入redux;</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>npm install react-redux
</span><span class='line'>
</span><span class='line'>npm install redux
</span></code></pre></td></tr></table></div></figure>


<p>关于redux，其实应用中所有的 state 都以一个对象树的形式储存在一个单一的 store 中。惟一改变 state 的办法是触发 action，一个描述发生什么的对象。</p>

<p>为了描述 action 如何改变 state 树，你需要编写 reducers，reducers 是一棵操作 state 的树，我用变量 <a href="https://github.com/TsaiKoga/lilu_movie/blob/master/redux/reducers/reducer.js">RootReducer</a> 命名更加形象。</p>

<p>通过写reducer，可以很好的管理 actions，这些 actions 操作形成了新的state，这样更加条理。可以看我的redux目录</p>

<blockquote><p>actions：用来fetch后台数据或者直接返回改变的内容</p>

<p>reducers：通过actions返回的数据，改变state</p>

<p>constants：每个actions的常量名</p>

<p>configureStore.js:通过传入reducers和初始的states，返回store（包含改变的states）</p></blockquote>

<p>然后前台app.js渲染之前，必须先通过<Provide>传入store；</p>

<p>即：通过 connect() 方法订阅了 reducers 树，触发 reducers 中某个 action，action 请求后台数据，返回 state 对象给添加订阅的 Provider store</p>

<br/>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
</pre></td><td class='code'><pre><code class='js'><span class='line'><span class="kr">const</span> <span class="nx">store</span> <span class="o">=</span> <span class="nx">configureStore</span><span class="p">(</span><span class="nb">window</span><span class="p">.</span><span class="nx">__INITIAL_STATE__</span><span class="p">)</span>
</span><span class='line'>
</span><span class='line'><span class="cm">/* 这里store存储某一时刻的state树，所以这里面通过action得到的states是不一样的</span>
</span><span class='line'><span class="cm"> * 例如：如果一开始给tags，后面action没有给tags，则不会有原来的初始值tags,所以不用担心数据冗余。</span>
</span><span class='line'><span class="cm"> */</span>
</span><span class='line'>
</span><span class='line'><span class="nx">ReactDOM</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span>
</span><span class='line'>  <span class="o">&lt;</span><span class="nx">Provider</span> <span class="nx">store</span><span class="o">=</span><span class="p">{</span><span class="nx">store</span><span class="p">}</span> <span class="o">&gt;</span>
</span><span class='line'>    <span class="o">&lt;</span><span class="nx">Router</span> <span class="nx">routes</span><span class="o">=</span><span class="p">{</span><span class="nx">routes</span><span class="p">}</span> <span class="nx">history</span><span class="o">=</span><span class="p">{</span><span class="nx">browserHistory</span><span class="p">}</span> <span class="o">/&gt;</span>
</span><span class='line'>  <span class="o">&lt;</span><span class="err">/Provider&gt;,</span>
</span><span class='line'>  <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">&#39;app&#39;</span><span class="p">)</span>
</span><span class='line'><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<br/>


<p>后台呢？也要相应根据么次fetch数据返回新的store。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
</pre></td><td class='code'><pre><code class='js'><span class='line'>  <span class="kr">const</span> <span class="nx">store</span> <span class="o">=</span> <span class="nx">configureStore</span><span class="p">(</span><span class="nx">initialState</span><span class="p">)</span>
</span><span class='line'>  <span class="kr">const</span> <span class="nx">state</span> <span class="o">=</span> <span class="nx">store</span><span class="p">.</span><span class="nx">getState</span><span class="p">()</span>
</span><span class='line'>  <span class="kr">const</span> <span class="nx">params</span> <span class="o">=</span> <span class="nb">Object</span><span class="p">.</span><span class="nx">assign</span><span class="p">(</span><span class="nx">req</span><span class="p">.</span><span class="nx">query</span><span class="p">,</span> <span class="nx">renderProps</span><span class="p">.</span><span class="nx">params</span><span class="p">)</span>
</span><span class='line'>
</span><span class='line'>  <span class="nx">fetchComponentDataBeforeRender</span><span class="p">(</span><span class="nx">store</span><span class="p">.</span><span class="nx">dispatch</span><span class="p">,</span> <span class="nx">renderProps</span><span class="p">.</span><span class="nx">components</span><span class="p">,</span> <span class="nx">params</span><span class="p">)</span>
</span><span class='line'>  <span class="p">.</span><span class="nx">then</span><span class="p">(()</span> <span class="o">=&gt;</span> <span class="p">{</span>
</span><span class='line'>    <span class="c1">// 这里redux的store给Provider，再通过mapStateToProps给对应的容器组件</span>
</span><span class='line'>    <span class="kr">const</span> <span class="nx">html</span> <span class="o">=</span> <span class="nx">renderToString</span><span class="p">(</span>
</span><span class='line'>      <span class="o">&lt;</span><span class="nx">Provider</span> <span class="nx">store</span><span class="o">=</span><span class="p">{</span><span class="nx">store</span><span class="p">}</span><span class="o">&gt;</span>
</span><span class='line'>        <span class="o">&lt;</span><span class="nx">RouterContext</span> <span class="p">{...</span><span class="nx">renderProps</span><span class="p">}</span> <span class="o">/&gt;</span>
</span><span class='line'>      <span class="o">&lt;</span><span class="err">/Provider&gt;</span>
</span><span class='line'>    <span class="p">)</span>
</span><span class='line'>    <span class="nx">res</span><span class="p">.</span><span class="nx">send</span><span class="p">(</span><span class="nx">renderFullPage</span><span class="p">(</span><span class="nx">html</span><span class="p">,</span> <span class="nx">store</span><span class="p">.</span><span class="nx">getState</span><span class="p">()));</span>
</span><span class='line'>  <span class="p">})</span>
</span></code></pre></td></tr></table></div></figure>


<p>有了后台传回来新的store，如何应用到前台组件呢？</p>

<br/>


<p>就在组件中引入connect：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='js'><span class='line'><span class="kr">import</span> <span class="p">{</span> <span class="nx">connect</span> <span class="p">}</span> <span class="nx">from</span> <span class="s1">&#39;react-redux&#39;</span>
</span></code></pre></td></tr></table></div></figure>




<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
</pre></td><td class='code'><pre><code class='js'><span class='line'><span class="kr">class</span> <span class="nx">MoviesGridList</span> <span class="kr">extends</span> <span class="nx">React</span><span class="p">.</span><span class="nx">Component</span> <span class="p">{</span>
</span><span class='line'><span class="p">...</span> <span class="p">....</span>
</span><span class='line'>  <span class="c1">// 将store最新的state.movies给props，</span>
</span><span class='line'>  <span class="kd">function</span> <span class="nx">mapStateToProps</span><span class="p">(</span><span class="nx">state</span><span class="p">,</span> <span class="nx">props</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>    <span class="kd">let</span> <span class="nx">tags</span> <span class="o">=</span> <span class="nx">props</span><span class="p">.</span><span class="nx">location</span><span class="p">.</span><span class="nx">query</span><span class="p">.</span><span class="nx">tags</span>
</span><span class='line'>    <span class="kd">let</span> <span class="nx">movies</span>
</span><span class='line'>    <span class="k">if</span> <span class="p">(</span><span class="nx">tags</span> <span class="o">===</span> <span class="kc">undefined</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'>      <span class="nx">movies</span> <span class="o">=</span> <span class="nx">state</span><span class="p">.</span><span class="nx">movies</span>
</span><span class='line'>    <span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
</span><span class='line'>      <span class="nx">movies</span> <span class="o">=</span> <span class="nx">getMoviesByTag</span><span class="p">(</span><span class="nx">state</span><span class="p">,</span> <span class="nx">tags</span><span class="p">)</span>
</span><span class='line'>    <span class="p">}</span>
</span><span class='line'>    <span class="k">return</span> <span class="p">{</span>
</span><span class='line'>      <span class="nx">tags</span><span class="o">:</span> <span class="nx">tags</span><span class="p">,</span>
</span><span class='line'>      <span class="nx">movies</span><span class="o">:</span> <span class="nx">movies</span>
</span><span class='line'>    <span class="p">}</span>
</span><span class='line'>  <span class="p">}</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="kr">export</span> <span class="k">default</span> <span class="nx">connect</span><span class="p">(</span><span class="nx">mapStateToProps</span><span class="p">)(</span><span class="nx">MoviesGridList</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<h2>总结</h2>

<hr />

<p>在数据为王的网络世界中，数据永远都是页面的核心，那么对于数据管理的模式；</p>

<p>react采用的是 <strong>单向数据流模式</strong>，</p>

<p>单向也就是数据只能从一个方向流向另外一个方向而不能反过来，</p>

<p>如果把dom想象成一颗树，<strong>单向数据流就是将数据自上向下的流动</strong>，为了让数据流到尽可能多的dom中，肯定要把数据尽可能放的高一点。这里的 <strong>根数据可以简单理解为state</strong>。</p>

<p>而对于流到 <strong>下面的数据，dom通过props接收</strong>。这样模式就很显而易见了，尽可能高的组件对state进行更新，子组件的props也会随即更新，数据单向流动，这时候如果想通过子组件来反向更新state，就要通过上层组件传递一个函数，在函数中通过setState等方法来达到反向数据的更新。</p>

<p>其实到这已经可以应付一些简单的应用了，但是对于复杂的应用，组件之间的数据通信有可能是交叉而又错综复杂的，这时候就希望通过一种统一的方式将数据好好管理起来，那么出现了redux。</p>

<p>使用 <strong>Redux 实现观察者模式，进行 订阅分发</strong>；</p>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[Rails 利用批量操作提速]]></title>
    <link href="https://TsaiKoga.github.com/blog/2016/08/21/rails-li-yong-pi-liang-cao-zuo-ti-su/"/>
    <updated>2016-08-21T14:29:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2016/08/21/rails-li-yong-pi-liang-cao-zuo-ti-su</id>
    <content type="html"><![CDATA[<h4><a href="#1.1">1.1 批量查找数据</a></h4>

<h5><a href="#1.2">1.2 操作代码</a></h5>

<h4><a href="#2.1">2.1 批量插入数据</a></h4>

<h5><a href="#2.2">2.2 INFILE文件插入数据</a></h5>

<h4><a href="#3.1">3.1 批量更改schema数据库</a></h4>

<h2 id="1.1">1.1 批量查找数据</h2>


<hr />

<p>由于之前一直在做后台的数据，其中有个任务是关于 财务库存 的页面.</p>

<blockquote><p>这个“财务库存”有产品和日期选项，您可以通过选择产品，查看它在某段时间内的库存价格等情况。</p>

<p>将采购入库单数据[PurchaseOrderBill]，销售出库单数据[OutStorageOrder]，异常取货和仓库调整单数据整合在一个页面；
根据日期排序来显示这个页面的内容，以及这些内容的成本价格变化，这里的价格根据这些取出来的数据进行排列后再进行运算得出。</p>

<p>项目中有近5w条产品记录，又要将“采购入库单”和“销售出库单”与 产品product进行关联查找，耗时挺大的。</p>

<p>这时候公司那边说要提供一次性下载所有产品的财务库存数据，不过不需要显示价格变化情况，直接显示最后一条价格结果就行了。</p></blockquote>

<p>近5w条的 product 产品关联(joins/includes)的单据进行计算价格，然后显示结果。
如何加快查找速度呢？</p>

<p>答案是进行 <strong>批量</strong> 查找。</p>

<h3 id="1.2">1.2 操作代码</h3>


<p>用代码说明吧，首先当然对于这么庞大的数据量，要进行 <strong>分页</strong> 处理：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">per_page</span> <span class="o">=</span> <span class="mi">100</span>
</span><span class='line'><span class="n">page</span> <span class="o">=</span> <span class="mi">0</span>
</span><span class='line'><span class="n">total_page</span> <span class="o">=</span> <span class="p">(</span><span class="no">Product</span><span class="o">.</span><span class="n">count</span><span class="o">.</span><span class="n">to_f</span> <span class="o">/</span> <span class="n">per_page</span><span class="p">)</span><span class="o">.</span><span class="n">ceil</span>
</span></code></pre></td></tr></table></div></figure>


<p>每一页进行 <strong>批量</strong> 操作：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">total_page</span><span class="o">.</span><span class="n">times</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">products</span> <span class="o">=</span> <span class="no">Product</span><span class="o">.</span><span class="n">limit</span><span class="p">(</span><span class="n">per_page</span><span class="p">)</span><span class="o">.</span><span class="n">offset</span><span class="p">(</span><span class="n">page</span> <span class="o">*</span> <span class="n">per_page</span><span class="p">)</span>
</span><span class='line'>  <span class="n">bill_items</span> <span class="o">=</span> <span class="n">bill_inventory_valuation_details</span> <span class="n">products</span>        <span class="c1"># 符合条件的采购入库单数据，此方法的查找也必须对 products 进行批量查找</span>
</span><span class='line'>  <span class="n">sell_items</span> <span class="o">=</span> <span class="n">sell_inventory_valuation_details</span> <span class="n">products</span>        <span class="c1"># 符合条件的销售出库数据</span>
</span><span class='line'>  <span class="n">package_items</span> <span class="o">=</span> <span class="n">package_inventory_valuation_details</span> <span class="n">products</span>  <span class="c1"># 异常出库数据</span>
</span><span class='line'>  <span class="n">adjust</span> <span class="o">=</span> <span class="n">adjust_inventory_valuation_details</span> <span class="n">products</span>          <span class="c1"># 调整仓库数据</span>
</span><span class='line'>  <span class="n">products</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">product</span><span class="o">|</span>
</span><span class='line'>    <span class="n">datas</span> <span class="o">=</span> <span class="o">[]</span>
</span><span class='line'>    <span class="n">datas</span> <span class="o">+=</span> <span class="n">bill_items</span><span class="o">[</span><span class="n">product</span><span class="o">.</span><span class="n">id</span><span class="o">].</span><span class="n">map</span><span class="p">{</span><span class="o">|</span><span class="n">item</span><span class="o">|</span> <span class="p">{</span><span class="nb">id</span><span class="p">:</span> <span class="n">item</span><span class="o">.</span><span class="n">id</span><span class="p">,</span> <span class="ss">quantity</span><span class="p">:</span> <span class="n">item</span><span class="o">.</span><span class="n">quantity</span><span class="p">,</span> <span class="ss">price</span><span class="p">:</span> <span class="n">item</span><span class="o">.</span><span class="n">price</span><span class="p">}}</span>
</span><span class='line'>    <span class="c1"># 对查出的数据进行处理，构造最终结果</span>
</span><span class='line'>    <span class="o">.</span><span class="n">.</span><span class="o">.</span> <span class="o">.</span><span class="n">.</span><span class="o">.</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>批量的产品分别进行采购单Bill,销售单Sell，包裹Package，还有调整库存单据Adjust的查询然后全部group_by产品ID，
最后将以产品ID来循环，将这个产品的所有单据组合一起，然后就可以算它的库存销售情况。
<strong>记住：代码循环永远比循环数据库操作要快的多</strong></p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">def</span> <span class="nf">bill_inventory_valuation_details</span> <span class="n">products</span>
</span><span class='line'>    <span class="n">bill_items</span> <span class="o">=</span> <span class="no">PurchaseOrderBillItem</span><span class="o">.</span><span class="n">joins</span><span class="p">(</span><span class="ss">:purchase_order_bill</span> <span class="o">=&gt;</span> <span class="ss">:purchase_order</span><span class="p">)</span><span class="o">.</span>
</span><span class='line'>                                       <span class="n">includes</span><span class="p">(</span><span class="ss">:purchase_order_bill</span> <span class="o">=&gt;</span> <span class="ss">:purchase_order</span><span class="p">)</span><span class="o">.</span>
</span><span class='line'>                                       <span class="n">where</span><span class="p">(</span><span class="s2">&quot;purchase_order_bills.status = ?&quot;</span><span class="p">,</span> <span class="ss">PurchaseOrderBill</span><span class="p">:</span><span class="ss">:STATUS</span><span class="o">[</span><span class="ss">:finished</span><span class="o">]</span><span class="p">)</span><span class="o">.</span>
</span><span class='line'>                                       <span class="n">where</span><span class="p">(</span><span class="s2">&quot;purchase_order_bills.date BETWEEN ? AND ?&quot;</span><span class="p">,</span> <span class="vi">@start_date</span><span class="p">,</span> <span class="vi">@end_date</span><span class="p">)</span><span class="o">.</span>
</span><span class='line'>                                       <span class="n">where</span><span class="p">(</span><span class="s2">&quot;purchase_order_bill_items.product_id IN (?)&quot;</span><span class="p">,</span> <span class="n">products</span><span class="o">.</span><span class="n">pluck</span><span class="p">(</span><span class="ss">:id</span><span class="p">))</span><span class="o">.</span>
</span><span class='line'>                                       <span class="n">group_by</span><span class="p">(</span><span class="o">&amp;</span><span class="ss">:product_id</span><span class="p">)</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'>
</span><span class='line'>  <span class="k">def</span> <span class="nf">sell_inventory_valuation_details</span> <span class="n">products</span>
</span><span class='line'>    <span class="n">sell_items</span> <span class="o">=</span> <span class="no">OutStorageOrderItem</span><span class="o">.</span><span class="n">joins</span><span class="p">(</span><span class="ss">:out_storage_order</span><span class="p">)</span><span class="o">.</span>
</span><span class='line'>                                     <span class="n">includes</span><span class="p">(</span><span class="ss">:out_storage_order</span><span class="p">)</span><span class="o">.</span>
</span><span class='line'>                                     <span class="n">where</span><span class="p">(</span><span class="s2">&quot;out_storage_orders.out_storage_order_type = ?&quot;</span><span class="p">,</span> <span class="mi">3</span><span class="p">)</span><span class="o">.</span>
</span><span class='line'>                                     <span class="n">where</span><span class="p">(</span><span class="s2">&quot;out_storage_orders.created_at BETWEEN ? AND ?&quot;</span><span class="p">,</span> <span class="vi">@start_date</span><span class="o">.</span><span class="n">beginning_of_day</span><span class="p">,</span> <span class="vi">@end_date</span><span class="o">.</span><span class="n">end_of_day</span><span class="p">)</span><span class="o">.</span>
</span><span class='line'>                                     <span class="n">where</span><span class="p">(</span><span class="s2">&quot;out_storage_orders.package_id IS NOT NULL OR out_storage_orders.package_group_id IS NOT NULL&quot;</span><span class="p">)</span><span class="o">.</span>
</span><span class='line'>                                     <span class="n">where</span><span class="p">(</span><span class="s2">&quot;out_storage_order_items.product_id IN (?)&quot;</span><span class="p">,</span> <span class="n">products</span><span class="o">.</span><span class="n">pluck</span><span class="p">(</span><span class="ss">:id</span><span class="p">))</span><span class="o">.</span>
</span><span class='line'>                                     <span class="n">group_by</span><span class="p">(</span><span class="o">&amp;</span><span class="ss">:product_id</span><span class="p">)</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'>
</span><span class='line'>  <span class="k">def</span> <span class="nf">adjust_inventory_valuation_details</span> <span class="n">products</span>
</span><span class='line'>    <span class="n">adjust</span> <span class="o">=</span> <span class="no">AdjustInventoryRecord</span><span class="o">.</span><span class="n">where</span><span class="p">(</span><span class="s2">&quot;the_date BETWEEN ? AND ?&quot;</span><span class="p">,</span> <span class="vi">@start_date</span><span class="p">,</span> <span class="vi">@end_date</span><span class="p">)</span><span class="o">.</span><span class="n">where</span><span class="p">(</span><span class="n">product_id</span><span class="p">:</span> <span class="n">products</span><span class="o">.</span><span class="n">pluck</span><span class="p">(</span><span class="ss">:id</span><span class="p">))</span><span class="o">.</span><span class="n">group_by</span><span class="p">(</span><span class="o">&amp;</span><span class="ss">:product_id</span><span class="p">)</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'>
</span><span class='line'>  <span class="k">def</span> <span class="nf">package_inventory_valuation_details</span> <span class="n">products</span>
</span><span class='line'>    <span class="n">package_items</span> <span class="o">=</span> <span class="no">PackageItem</span><span class="o">.</span><span class="n">eager_load</span><span class="p">(</span><span class="ss">:package</span><span class="p">)</span><span class="o">.</span><span class="n">where</span><span class="p">(</span><span class="n">product_id</span><span class="p">:</span> <span class="n">products</span><span class="o">.</span><span class="n">pluck</span><span class="p">(</span><span class="ss">:id</span><span class="p">))</span><span class="o">.</span>
</span><span class='line'>                                                  <span class="n">where</span><span class="p">(</span><span class="s2">&quot;packages.state = ?&quot;</span><span class="p">,</span> <span class="ss">Package</span><span class="p">:</span><span class="ss">:STATE_VALUES</span><span class="o">[</span><span class="ss">:processed</span><span class="o">]</span><span class="p">)</span><span class="o">.</span>
</span><span class='line'>                                                  <span class="n">where</span><span class="p">(</span><span class="s2">&quot;packages.dropship = ?&quot;</span><span class="p">,</span> <span class="kp">false</span><span class="p">)</span><span class="o">.</span>
</span><span class='line'>                                                  <span class="n">where</span><span class="p">(</span><span class="s2">&quot;packages.shipped_at &gt;= ? AND packages.shipped_at &lt;= ?&quot;</span><span class="p">,</span> <span class="vi">@start_date</span><span class="p">,</span> <span class="vi">@end_date</span><span class="p">)</span><span class="o">.</span><span class="n">group_by</span><span class="p">(</span><span class="o">&amp;</span><span class="ss">:product_id</span><span class="p">)</span>
</span><span class='line'>  <span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>这样原先没有进行批量操作会耗时接近12个小时，使用了批量操作后仅为2个多小时。</p>

<h2 id="2.1">2.1 批量插入数据</h2>


<hr />

<p>当你要对大量数据进行插入数据库的操作时，一条条插入将是及其愚蠢的行为。如何进行批量插入呢？</p>

<p>可以先看看这篇文章：<a href="https://www.coffeepowered.net/2009/01/23/mass-inserting-data-in-rails-without-killing-your-performance/">Mass inserting data in Rails without killing your performance</a></p>

<p>这篇文章提到 Rails 快速插入数据的四种方法：</p>

<ol>
<li><p>Use transactions</p></li>
<li><p>Get down and dirty with the raw SQL</p></li>
<li><p>A single mass insert</p></li>
<li><p>Use INSERT statements with multiple VALUES lists with ar-extensions OR activerecord-import</p></li>
</ol>


<p>第四种方式是AR方式的70倍左右，而公司后台使用的正是 activerecord-import,
做法很简单，先将数据创建 <strong>存于内存</strong>，然后批量 import <strong>插入</strong> 数据库：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="p">(</span><span class="n">controller</span><span class="o">.</span><span class="n">action_methods</span><span class="o">.</span><span class="n">to_a</span> <span class="o">-</span> <span class="n">excepts</span><span class="p">)</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">action</span><span class="o">|</span>
</span><span class='line'>  <span class="n">need_imports</span> <span class="o">&lt;&lt;</span> <span class="no">Permission</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="ss">subject</span><span class="p">:</span> <span class="n">subject</span><span class="p">,</span> <span class="ss">action</span><span class="p">:</span> <span class="n">action</span><span class="p">,</span> <span class="ss">description</span><span class="p">:</span> <span class="s2">&quot;</span><span class="si">#{</span><span class="n">action</span><span class="o">.</span><span class="n">humanize</span><span class="si">}</span><span class="s2"> of </span><span class="si">#{</span><span class="n">subject</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">)</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'><span class="no">Permission</span><span class="o">.</span><span class="n">import</span> <span class="n">need_imports</span>
</span></code></pre></td></tr></table></div></figure>


<p>这样已经很快了，还有更快的吗？</p>

<h3 id="2.2">2.2 INFILE文件插入数据 </h3>


<p>From MySQL Doc:</p>

<blockquote><p>When loading a table from a text file, use LOAD DATA INFILE. This is usually 20 times faster than using INSERT statements</p></blockquote>

<p>SQL语句：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="p">(</span><span class="mi">15955</span><span class="o">.</span><span class="mi">1</span><span class="n">ms</span><span class="p">)</span>  <span class="no">LOAD</span> <span class="no">DATA</span> <span class="no">LOCAL</span> <span class="no">INFILE</span> <span class="s1">&#39;/Users/tsaikoga/out_storage_orders.txt&#39;</span>
</span><span class='line'><span class="no">REPLACE</span> <span class="no">INTO</span> <span class="no">TABLE</span> <span class="n">out_storage_orders</span> <span class="no">FIELDS</span> <span class="no">TERMINATED</span> <span class="no">BY</span> <span class="s1">&#39;,&#39;</span> <span class="p">(</span><span class="sb">`id`</span><span class="p">,</span><span class="sb">`warehouse_id`</span><span class="p">,</span><span class="sb">`destination_id`</span><span class="p">,</span><span class="sb">`user_id`</span><span class="p">,</span><span class="sb">`out_storage_order_type`</span><span class="p">,</span><span class="sb">`out_storage_reason_type`</span><span class="p">,</span><span class="sb">`status`</span><span class="p">,</span><span class="sb">`quantity`</span><span class="p">,</span><span class="sb">`package_id`</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>插入行数：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>wc -l &lt; /Users/tsaikoga/out_storage_orders.txt
</span><span class='line'>100000
</span></code></pre></td></tr></table></div></figure>




<h3 id="3.1">3.1 批量更改schema数据库</h3>


<hr />

<p>你有没有发现，当你某张表的数据非常非常多的时候，你想要更改其中一个字段的类型，然后执行 migrate ；
执行时间非常长，你厌倦了等待，只好 ctrl+c 撤销了migrate，但是实际上数据库中的记录已经有很大一部分改变了字段的类型。
这时候你想再migrate，会出现这种类型的字段已存在的提示。（当然你可以利用mysql的界面工具或直接到mysql更改字段类型进行拯救）</p>

<p>这里提供一个 Rails 的方法，将数据大批量进行更改。
比方说，以下是一段更改 orders 表的 shipping_first_name shipping_last_name 名称的方法：</p>

<pre><code>rename_column :orders, "shipping_first_name", "origin_shipping_first_name"
rename_column :orders, "shipping_last_name", "origin_shipping_last_name"
</code></pre>

<p>执行migrate用时非常长，还不如使用如下代码：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">class</span> <span class="nc">RenameOldOrderAddressRelatedColumn</span> <span class="o">&lt;</span> <span class="ss">ActiveRecord</span><span class="p">:</span><span class="ss">:Migration</span>
</span><span class='line'>  <span class="k">def</span> <span class="nf">up</span>
</span><span class='line'>    <span class="n">change_table</span><span class="p">(</span><span class="ss">:orders</span><span class="p">,</span> <span class="ss">:bulk</span> <span class="o">=&gt;</span> <span class="kp">true</span><span class="p">)</span> <span class="k">do</span> <span class="o">|</span><span class="n">t</span><span class="o">|</span>
</span><span class='line'>      <span class="n">t</span><span class="o">.</span><span class="n">rename</span> <span class="ss">:order_status_code_id</span><span class="p">,</span> <span class="ss">:state</span>
</span><span class='line'>      <span class="n">t</span><span class="o">.</span><span class="n">remove</span> <span class="ss">:in_process</span>
</span><span class='line'>      <span class="o">[</span><span class="ss">:first_name</span><span class="p">,</span>
</span><span class='line'>       <span class="ss">:last_name</span><span class="p">,</span>
</span><span class='line'>       <span class="ss">:country</span><span class="p">,</span>
</span><span class='line'>       <span class="ss">:state</span><span class="o">].</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">column</span><span class="o">|</span>
</span><span class='line'>        <span class="n">t</span><span class="o">.</span><span class="n">rename</span> <span class="s2">&quot;shipping_</span><span class="si">#{</span><span class="n">column</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">,</span> <span class="s2">&quot;origin_shipping_</span><span class="si">#{</span><span class="n">column</span><span class="si">}</span><span class="s2">&quot;</span>
</span><span class='line'>      <span class="k">end</span>
</span><span class='line'>    <span class="k">end</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>以上代码只生成一句 SQL 语句，数据库迁移时间大大减少。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="no">ALTER</span> <span class="no">TABLE</span> <span class="sb">`orders`</span> <span class="no">DROP</span> <span class="sb">`in_process`</span><span class="p">,</span> <span class="no">CHANGE</span> <span class="sb">`shipping_first_name`</span> <span class="sb">`origin_shipping_first_name`</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">50</span><span class="p">)</span> <span class="no">DEFAULT</span> <span class="no">NULL</span><span class="p">,</span> <span class="no">CHANGE</span> <span class="sb">`shipping_last_name`</span> <span class="sb">`origin_shipping_last_name`</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">50</span><span class="p">)</span> <span class="no">DEFAULT</span> <span class="no">NULL</span><span class="p">,</span> <span class="no">CHANGE</span> <span class="sb">`shipping_country`</span> <span class="sb">`origin_shipping_country`</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">255</span><span class="p">)</span> <span class="no">DEFAULT</span> <span class="no">NULL</span><span class="p">,</span> <span class="no">CHANGE</span> <span class="sb">`shipping_state`</span> <span class="sb">`origin_shipping_state`</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">255</span><span class="p">)</span> <span class="no">DEFAULT</span> <span class="no">NULL</span><span class="o">.</span><span class="n">.</span><span class="o">.</span>
</span></code></pre></td></tr></table></div></figure>


<p>相关文档：</p>

<p><a href="http://dev.mysql.com/doc/refman/5.5/en/load-data.html">http://dev.mysql.com/doc/refman/5.5/en/load-data.html</a>
<a href="http://dev.mysql.com/doc/refman/5.5/en/insert-speed.html">http://dev.mysql.com/doc/refman/5.5/en/insert-speed.html</a></p>

<p>总结，对于大数据一定要进行批量处理。</p>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[公司项目中 Git 的使用方法]]></title>
    <link href="https://TsaiKoga.github.com/blog/2016/08/06/gong-si-xiang-mu-zhong-git-de-shi-yong-fang-fa/"/>
    <updated>2016-08-06T16:10:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2016/08/06/gong-si-xiang-mu-zhong-git-de-shi-yong-fang-fa</id>
    <content type="html"><![CDATA[<p>Git 是开源的分布式版本控制器，用于敏捷高效地处理任何或小或大的项目。</p>

<p>它被应用到很多 Rails 开发项目中。 公司对于 Git 也有适合的一套用法。</p>

<h4>背景</h4>

<hr />

<p>首先我来介绍一下公司的大致情况，然后阐述一下公司如何用Git进行工作：</p>

<p>我们公司是一家外企电商平台，产品在国外销售，技术部在中国，所以会有时差。面对这类问题，我们技术部这边对项目进行开发完善，
确定每周二的一个时间点为项目上线时间（因为这个时间点用户量极少），所有大改动和新功能都会在本周的这个时间点上线，我们称之为【常规上线】。
对于项目突然出现的 Bug ，或是上线后出现的 Bug，我们也会更改然后上线，这次上线属于当天的紧急上线，我们称之为【紧急上线】，取名为Hot Fix。</p>

<p>OK，接着来看看我们是如何使用 Git 进行如上的上线操作的。</p>

<h3>操作流程</h3>

<hr />

<h4>分支介绍</h4>

<p>先来看看我们项目主要的分支吧：</p>

<ul>
<li><p>master 主分支，用来部署周二的常规上线。</p></li>
<li><p>release 发布分支，这个分支的代码一定是生产环境下的分支（代码最新），用于切除 Hotfix 分支，作紧急上线处理。</p></li>
<li><p>testing 常规上线的测试分支，这里的代码用于测试，周二常规上线后可以删除后重建；不与master相同，测试完此分支与master分支无关；
用于当测试出现 BUG，修复很多次，最后测试通过；本地可以将最后通过的commits都合并为一个commit提交到master，保证commit的整洁，减少冲突。</p></li>
</ul>


<h4>常规上线</h4>

<p>接着，我们来看看如何常规上线，假设这周我有一个任务要完成，从 master 切出一个分支叫做 develop</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>git checkout -b develop
</span><span class='line'>git commit -m <span class="s2">&quot;First Commit&quot;</span>
</span><span class='line'>git push origin develop
</span></code></pre></td></tr></table></div></figure>


<p>然后周二正式上线，我们周一先将自己的分支本地测完，然后“合并”到公共的 testing 分支【记住是merge哦，不是rebase】；</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>git checkout testing                <span class="c"># from develop to testing</span>
</span><span class='line'><span class="c"># git merge develop                 # 这里一般是发到 github 上给别人 pr，或是发到gitlab上给别人 mr</span>
</span><span class='line'>git push origin testing             <span class="c"># 如果是通过 gitlab/github mr/pr 后，这里将是 git pull origin testing</span>
</span><span class='line'><span class="nv">BRANCH</span><span class="o">=</span>testing cap staging deploy   <span class="c"># 这里的 BRANCH 是通过 .bashrc 设置环境变量，deploy/staging.rb 中 set :branch, ENV[&quot;BRANCH&quot;] || &quot;master&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<h4>注意事项 （merge 和 rebase）</h4>

<blockquote><p>有个问题需要注意，曾经我将我的代码rebase到testing上；</p>

<pre><code>git checkout testing
git rebase develop
</code></pre>

<p>rebase 会将 testing 和 develop 两个分支中的commit整理成 testing 一个分支，但是当两个分支中有一个commit发生冲突的时候
<img src="https://TsaiKoga.github.com/images/posts/2016-08-06/git-rebase.png" title="rebase的图示" alt="git rebase" /></p>

<p>这个冲突如上图，来自于 develop 的 commit，你将它 rebase 到了 testing 上，正当你觉得一切顺利的时候；</p>

<p>你想要 push 你的代码到远程的 testing，你会发现需要 pull 代码，然而当你 pull 代码后，你又发现原来的冲突，然后解决冲突，然后再 pull 代码，这样无限循环下去&hellip;</p>

<p>这是因为远程的 testing 就是没解决冲突前的 testing 分支，你 rebase 后解决冲突的 commit 是 develop 的commit，这样你再次拉代码下来，冲突又再次出现了。</p></blockquote>

<p>所以，使用“merge”！这里 merge 后，develop 的 commit3 会与 testing 产生冲突，解决完冲突后，merge 不像 rebase 会把解决完的放在原来的 commit3 上，而是你需要
新提交一个解决冲突后的 commit【我们叫它commit4】，这样就 pull 的代码遇到 commit4，发现已被解决，就没有冲突了。</p>

<h4>紧急上线 Hotfix</h4>

<p>看到上面的常规上线，我们结束了周二的工作任务；周三来了，你来到办公室，发现昨天上线的内容还需要修改，并且必须在今天上线。这时候我们需要如下分支：</p>

<ul>
<li><p>release 分支， 周二从 master 分支部署到正式服务器后，将 master 代码 merge release 分支，release上的代码即代表着线上的最新代码。</p></li>
<li><p>hotfix160803 分支，从名字可以看出 hotfix + 日期，这个是从 release 切出来的，像testing分支一样，让所有要紧急发布的程序员将今天自己的分支合到这里进行测试。</p></li>
</ul>


<p>具体操作就是
1. 首先我们从 release 下载线上的代码 <code>git pull origin release:release</code>
2. release 分支切出一个 hotfix 分支 <code>git checkout -b hotfix160803</code>
3. 提交 hotfix160803 到远程，让大家可以合并代码
4. 建立自己的紧急开发分支 <code>git checkout -b hotfix-dev</code></p>

<p>如果已经有人提交了hotfix160803，则只需要 pull 下来，然后建立自己的分支开发。</p>

<p>接下来改完代码后的操作其实和常规上线一样。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>git push hotfix-dev
</span></code></pre></td></tr></table></div></figure>


<p>gitlab 或 github 上 mr 或 pr</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>git checkout hotfix160803
</span><span class='line'>git pull hotfix160803 <span class="c"># 将合并后的代码拉下来</span>
</span><span class='line'><span class="nv">BRANCH</span><span class="o">=</span>hotfix160803 cap staging deploy
</span></code></pre></td></tr></table></div></figure>


<p>测试完毕后，将 hotfix160803 merge 到 release，发布release。</p>

<p>忙碌的一天就结束了。</p>

<h4>关于 Capistrano 的代码</h4>

<p>你的代码放在 gitlab 上面，项目运行在某个服务器A上，你将代码提交到 gitlab 上，然后 cap deploy；
其实cap deploy 是通过 clone 你的 gitlab 上的代码到服务器A上的</p>

<p>关于抽出逻辑，制作一个功能，其他传入简单参数，
关于方法里面，只有if，那干脆将if放方法外面；
关于需求，通过每个条件都列出来检查。
对于更改数据，记住留份log作为备份，将数据记录下来，以便回滚。</p>

<h4>经常使用的 Git 命令</h4>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>git checkout -b testing         <span class="c"># 新建分支testing 并切换到上面</span>
</span><span class='line'>
</span><span class='line'>git commit -m <span class="s2">&quot;Koga&quot;</span>            <span class="c"># commit</span>
</span><span class='line'>git commit --amend              <span class="c"># 将 add 的新修改也提交到之前的commit，并且可以更改commit名称</span>
</span><span class='line'>
</span><span class='line'>git pull origin master:master   <span class="c"># 拉远程的master到本地master，如果本地没有，则新建并拉代码下来，并且所在的分支也会拉master的内容下来，可以将其add 后checkout掉</span>
</span><span class='line'>git push origin master          <span class="c"># 提交到远程master分支，如果git push -f origin master，将强制提交</span>
</span><span class='line'>
</span><span class='line'>git rebase master               <span class="c"># 将当前分支与master合成一条</span>
</span><span class='line'>git reset HEAD~1                <span class="c"># 重置 上一个 commit，但是修改内容还是保留，只是还没commit</span>
</span><span class='line'>git merge master                <span class="c"># 将master合并到当前分支</span>
</span><span class='line'>
</span><span class='line'>git branch                      <span class="c"># 显示所有分支</span>
</span><span class='line'>git branch -D testing           <span class="c"># 删除 testing 分支</span>
</span><span class='line'>git branch -m dev               <span class="c"># 更改分支名称</span>
</span><span class='line'>
</span><span class='line'>git stash                       <span class="c"># 将更改内容暂存</span>
</span><span class='line'>git stash pop                   <span class="c"># 将暂存内容弹出</span>
</span><span class='line'>git stash clear                 <span class="c"># 清除暂存内容</span>
</span></code></pre></td></tr></table></div></figure>


<p>让 bash 显示当前Git的分支及当前路径（如果有python的virtualenv，也显示在开头）：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="c">##############################################</span>
</span><span class='line'><span class="c"># shell obtain the git&#39;s current branch name #</span>
</span><span class='line'><span class="c">##############################################</span>
</span><span class='line'>find_git_branch<span class="o">()</span> <span class="o">{</span>
</span><span class='line'>  <span class="nb">local </span><span class="nv">dir</span><span class="o">=</span>. head
</span><span class='line'>  <span class="k">until</span> <span class="o">[</span> <span class="s2">&quot;$dir&quot;</span> -ef / <span class="o">]</span>; <span class="k">do</span>
</span><span class='line'><span class="k">    if</span> <span class="o">[</span> -f <span class="s2">&quot;$dir/.git/HEAD&quot;</span> <span class="o">]</span>; <span class="k">then</span>
</span><span class='line'><span class="k">      </span><span class="nv">head</span><span class="o">=</span><span class="k">$(</span>&lt; <span class="s2">&quot;$dir/.git/HEAD&quot;</span><span class="k">)</span>
</span><span class='line'>      <span class="k">if</span> <span class="o">[[</span> <span class="nv">$head</span> <span class="o">=</span> ref:<span class="se">\ </span>refs/heads/* <span class="o">]]</span>; <span class="k">then</span>
</span><span class='line'><span class="k">        </span><span class="nv">git_branch</span><span class="o">=</span><span class="s2">&quot;[${head#*/*/}]&quot;</span>
</span><span class='line'>      <span class="k">elif</span> <span class="o">[[</span> <span class="nv">$head</span> !<span class="o">=</span> <span class="s1">&#39;&#39;</span> <span class="o">]]</span>; <span class="k">then</span>
</span><span class='line'><span class="k">        </span><span class="nv">git_branch</span><span class="o">=</span><span class="s2">&quot;[no branch]&quot;</span>
</span><span class='line'>      <span class="k">else</span>
</span><span class='line'><span class="k">        </span><span class="nv">git_branch</span><span class="o">=</span><span class="s2">&quot;[unknow]&quot;</span>
</span><span class='line'>      <span class="k">fi</span>
</span><span class='line'><span class="k">      return</span>
</span><span class='line'><span class="k">    fi</span>
</span><span class='line'><span class="k">    </span><span class="nv">dir</span><span class="o">=</span><span class="s2">&quot;../$dir&quot;</span>
</span><span class='line'>  <span class="k">done</span>
</span><span class='line'><span class="k">  </span><span class="nv">git_branch</span><span class="o">=</span><span class="s1">&#39;&#39;</span>
</span><span class='line'><span class="o">}</span>
</span><span class='line'><span class="nv">PROMPT_COMMAND</span><span class="o">=</span><span class="s2">&quot;find_git_branch; $PROMPT_COMMAND&quot;</span>
</span><span class='line'><span class="nb">export </span><span class="nv">PS1</span><span class="o">=</span><span class="s2">&quot;(`basename \&quot;$VIRTUAL_ENV\&quot;`)\u@\h:\w\$git_branch\$ &quot;</span>
</span></code></pre></td></tr></table></div></figure>

]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[Atom 快捷键使用大全]]></title>
    <link href="https://TsaiKoga.github.com/blog/2016/05/06/atomkuai-jie-jian-shi-yong-da-quan/"/>
    <updated>2016-05-06T11:36:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2016/05/06/atomkuai-jie-jian-shi-yong-da-quan</id>
    <content type="html"><![CDATA[<h3><a href="#1">1. 快捷键标识</a></h3>

<h3><a href="#2">2. 内容</a></h3>

<h2 id="1">快捷键标识</h2>


<p>⌘ : Command key</p>

<p>⌃ : Control key</p>

<p>⌫ : Delete key</p>

<p>← : Left arrow key</p>

<p>→ : Right arrow key</p>

<p>↑ : Up arrow key</p>

<p>↓ : Down arrow key</p>

<p>⌥ : Option or Alt key</p>

<p>↩ : Return or Enter key</p>

<p>⇧ : Shift key</p>

<br/>


<p>终端输入atom ./ 将会用 atom 打开当前目录</p>

<h2 id="2">内容</h2>


<p><a href="#2.1">2.1. 命令板</a></p>

<p><a href="#2.2">2.2. 配置</a></p>

<p><a href="#2.3">2.3. 项目任务</a></p>

<p><a href="#2.4">2.4. 自动补全</a></p>

<p><a href="#2.5">2.5. 书签</a></p>

<p><a href="#2.6">2.6. 括号 </a></p>

<p><a href="#2.7">2.7. 代码折叠</a></p>

<p><a href="#2.8">2.8. 代码导航和管理</a></p>

<p><a href="#2.9">2.9. 字符变化</a></p>

<p><a href="#2.10">2.10. 注释</a></p>

<p><a href="#2.11">2.11. 编辑器视图任务</a></p>

<p><a href="#2.12">2.12. 文件任务</a></p>

<p><a href="#2.13">2.13. 查找和替换</a></p>

<p><a href="#2.14">2.14. 字体任务</a></p>

<p><a href="#2.15">2.15. 语法</a></p>

<p><a href="#2.16">2.16. 搜索任务</a></p>

<br/>




<h3 id="2.1">命令板</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>打开命令板</td>
      <td>⌘-⇧-p</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.2">配置</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>打开配置编辑器</td>
      <td>⌘-,</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.3">项目任务</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>隐藏应用</td>
      <td>⌘-h</td>
    </tr>
    <tr>
      <td>隐藏其他应用</td>
      <td>⌥-⌘-h</td>
    </tr>
    <tr>
      <td>最小化应用</td>
      <td>⌘-m</td>
    </tr>
    <tr style="color: red;">
      <td>新建文件</td>
      <td>⌘-n</td>
    </tr>
    <tr>
      <td>新建窗口</td>
      <td>⌘-⇧-n</td>
    </tr>
    <tr>
      <td>打开应用</td>
      <td>⌘-o</td>
    </tr>
    <tr>
      <td>打开Dev</td>
      <td>⇧-⌘-o</td>
    </tr>
    <tr>
      <td>退出Atom</td>
      <td>⌘-q</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.4">自动补全</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>打开配置编辑器</td>
      <td>⌘-,</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.5">书签</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>切换书签</td>
      <td>⌘-F2</td>
    </tr>
    <tr>
      <td>查看所有书签</td>
      <td>⌃-F2</td>
    </tr>
    <tr>
      <td>跳到下一个书签</td>
      <td>F2</td>
    </tr>
    <tr>
      <td>跳到上一个书签</td>
      <td>⇧-F2</td>
    </tr>
    <tr>
      <td>清除所有书签</td>
      <td>⌘-⇧-F2</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.6">括号</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>寻找匹配的括号</td>
      <td>⌃-m</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.7">代码折叠</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr style="color: red;">
      <td>合上代码</td>
      <td>⌥-⌘-[</td>
    </tr>
    <tr style="color: red;">
      <td>展开代码</td>
      <td>⌥-⌘-]</td>
    </tr>
    <tr>
      <td>在缩排第N级合上代码</td>
      <td>⌘-k cmd-N</td>
    </tr>
    <tr>
      <td>合上所选的文本</td>
      <td>⌥-⌘-⌃-f</td>
    </tr>
    <tr style="color: red;">
      <td>展开所有代码</td>
      <td>⌥-⌘-}</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.8">代码导航和管理</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>裁剪到行末</td>
      <td>⌃-k</td>
    </tr>
    <tr>
      <td>删除到单词起始位</td>
      <td>⌥-⌫</td>
    </tr>
    <tr>

      <td>删除到单词末尾</td>
      <td>⌥-d</td>
    </tr>
    <tr>
      <td>删除行</td>
      <td>⌃-⇧-k</td>
    </tr>
    <tr>
      <td>复制行</td>
      <td>⌘-⇧-d</td>
    </tr>
    <tr>
      <td>跳到行</td>
      <td>⌃-g</td>
    </tr>
    <tr>
      <td>跳到匹配的括号</td>
      <td>⌃-m</td>
    </tr>
    <tr>
      <td>缩进所选文字</td>
      <td>⌘-]</td>
    </tr>
    <tr>
      <td>前进所选文字</td>
      <td>⌘-[</td>
    </tr>
    <tr>
      <td>加入行</td>
      <td>⌘-j</td>
    </tr>
    <tr>
      <td>移动单词到开头</td>
      <td>⌥-b</td>
    </tr>
    <tr>
      <td>移动单词到末尾</td>
      <td>⌥-f</td>
    </tr>
    <tr>
      <td>移动到行起始位</td>
      <td>⌃-a</td>
    </tr>
    <tr>
      <td>移动到行末</td>
      <td>⌃-e</td>
    </tr>
    <tr>
      <td>移动行到上面</td>
      <td>⌘-⌃-↑</td>
    </tr>
    <tr>
      <td>移动行到下面</td>
      <td>⌘-⌃-↓</td>
    </tr>
    <tr>
      <td>移动文件到顶部</td>
      <td>⌘-↑</td>
    </tr>
    <tr>
      <td>移动文件到底部</td>
      <td>⌘-↓</td>
    </tr>
    <tr>
      <td>移动到行的一个字符</td>
      <td>⌘-←</td>
    </tr>
    <tr>
      <td>移动到行的最后一个字符</td>
      <td>⌘-→</td>
    </tr>
    <tr>
      <td>移动左边的字符</td>
      <td>⌘-⌃-b</td>
    </tr>
    <tr>
      <td>移动右边的字符</td>
      <td>⌘-⌃-f</td>
    </tr>
    <tr>
      <td>移动到单词的开头</td>
      <td>⌥-⇧-b</td>
    </tr>
    <tr>
      <td>移动到单词的末尾</td>
      <td>⌥-⇧-f</td>
    </tr>
    <tr>
      <td>移动整个单词</td>
      <td>⌃-⇧-w</td>
    </tr>
    <tr>
      <td>选择到行的第一个字符</td>
      <td>⌥-⇧-a</td>
    </tr>
    <tr>
      <td>选择到行的最后一个字符</td>
      <td>⌥-⇧-e</td>
    </tr>
    <tr>
      <td>选择到相同的位置</td>
      <td>⌥-⇧-n</td>
    </tr>
    <tr>
      <td>选择到上一行相同的位置</td>
      <td>⌥-⇧-p</td>
    </tr>
    <tr>
      <td>选择到文件头</td>
      <td>⌘-⇧-↑</td>
    </tr>
    <tr>
      <td>选择到文件尾</td>
      <td>⌘-⇧-↓</td>
    </tr>
    <tr>
      <td>选择全部</td>
      <td>⌘-a</td>
    </tr>
    <tr>
      <td>选择到下一个</td>
      <td>⌘-d</td>
    </tr>
    <tr>
      <td>选择行</td>
      <td>⌘-L</td>
    </tr>
    <tr>
      <td>切换注释</td>
      <td>⌘-/</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.9">字符变化</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr style="color: red;">
      <td>将Tab变成空格</td>
      <td>⌥-⌘-[</td>
    </tr>
    <tr style="color: red;">
      <td>将空格变成Tab</td>
      <td>⌥-⌘-]</td>
    </tr>
    <tr>
      <td>变成大写</td>
      <td>⌘-k-u</td>
    </tr>
    <tr>
      <td>变成小写</td>
      <td>⌘-k-L</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.10">注释</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr style="color: red;">
      <td>切换注释</td>
      <td>⌘-/</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.11">编辑器视图任务</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>垂直拆分面板</td>
      <td>⌘-k-↓</td>
    </tr>
    <tr>
      <td>水平拆分面板</td>
      <td>⌘-k-→</td>
    </tr>
    <tr>
      <td>垂直导航面板</td>
      <td>⌘-k ⌘-↓</td>
    </tr>
    <tr>
      <td>水平导航面板</td>
      <td>⌘-k ⌘-→</td>
    </tr>
    <tr>
      <td>切换全屏</td>
      <td>⌃-⌘-f</td>
    </tr>
    <tr style="color: red;">
      <td>切换树</td>
      <td>⌘-\</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.12">文件任务</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>模糊搜索文件</td>
      <td>⌘-t</td>
    </tr>
    <tr>
      <td>寻找并打开文件</td>
      <td>⌘-b</td>
    </tr>
    <tr>
      <td>找最近更改但是还未跟踪的文件（git）</td>
      <td>⌘-⇧-b</td>
    </tr>
    <tr>
      <td>打开树</td>
      <td>⌃-0</td>
    </tr>
    <tr>
      <td>切换到树</td>
      <td>⌘-&#92;</td>
    </tr>
    <tr style="color: red;">
      <td>增加文件</td>
      <td>a</td>
    </tr>
    <tr style="color: red;">
      <td>移动文件</td>
      <td>m</td>
    </tr>
    <tr style="color: red;">
      <td>删除文件</td>
      <td>⌫</td>
    </tr>
    <tr>
      <td>重新打开文件</td>
      <td>⌘-⇧-t</td>
    </tr>
  </tbody>
</table>




<br/>


<h3 id="2.13">查找和替换</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>在当前文件查找字符串</td>
      <td>⌘-f</td>
    </tr>
    <tr>
      <td>整个项目中查找字符串</td>
      <td>⇧-⌘-f</td>
    </tr>
    <tr>
      <td>跳到匹配的字符串</td>
      <td>⌘-g</td>
    </tr>
    <tr style="color: red;">
      <td>跳到前面匹配的字符串</td>
      <td>⇧-⌘-g</td>
    </tr>
    <tr>
      <td>跳到后面匹配的字符串</td>
      <td>⌘-d</td>
    </tr>
    <tr style="color: red;">
      <td>选择所有匹配的字符串</td>
      <td>⌃-⌘-g</td>
    </tr>
    <tr>
      <td>替换当前文件的字符串</td>
      <td>⌥-⌘-f</td>
    </tr>
  </tbody>
</table>




<br/>




<h3 id="2.14">字体任务</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>增加字体大小</td>
      <td>cmd-+</td>
    </tr>
    <tr>
      <td>减少字体大小</td>
      <td>cmd—</td>
    </tr>
  </body>
</table>




<br/>




<h3 id="2.15">语法</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>选择语法</td>
      <td>⌃-⇧-L</td>
    </tr>
  </tbody>
</table>




<br/>




<h3 id="2.16">搜索任务</h3>


<hr />

<table style="padding: 10px; width: 100%;">
  <thead>
    <tr>
      <th>任务</th>
      <th>按键</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>搜索符号</td>
      <td>⌘-r</td>
    </tr>
    <tr>
      <td>整个项目中搜索符号</td>
      <td>⌘-⇧-r</td>
    </tr>
  </tbody>
</table>

]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[Routing]]></title>
    <link href="https://TsaiKoga.github.com/blog/2015/08/03/routing/"/>
    <updated>2015-08-03T14:55:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2015/08/03/routing</id>
    <content type="html"><![CDATA[<h3>目录：</h3>

<h4><a href="#2.1">2.1 路由的两个目标</a></h4>

<h4><a href="#2.2">2.2 routes.rb文件</a></h4>

<h5><a href="#2.2.1">2.2.1 路由规则</a></h5>

<h5><a href="#2.2.2">2.2.2 限制请求方法</a></h5>

<h5><a href="#2.2.3">2.2.3 URL 模式</a></h5>

<h5><a href="#2.2.4">2.2.4 段键</a></h5>

<h5><a href="#2.2.5">2.2.5 聚焦于id字段</a></h5>

<h5><a href="#2.2.6">2.2.6 可选的段键</a></h5>

<h5><a href="#2.2.7">2.2.7 重定向路由</a></h5>

<h5><a href="#2.2.8">2.2.8 格式段format</a></h5>

<h5><a href="#2.2.9">2.2.9 路由作为Rack的端点</a></h5>

<h5><a href="#2.2.10">2.2.10 接收头</a></h5>

<h5><a href="#2.2.11">2.2.11 段键约束</a></h5>

<h5><a href="#2.2.12">2.2.12 根路由</a></h5>

<h4><a href="#2.3">2.3 路径匹配</a></h4>

<h4><a href="#2.4">2.4 命名路由</a></h4>

<h5><a href="#2.4.1">2.4.1 创建一个命名路由</a></h5>

<h5><a href="#2.4.2">2.4.2 name_path vs name_url</a></h5>

<h5><a href="#2.4.3">2.4.3 给你的路由命名</a></h5>

<h5><a href="#2.4.4">2.4.4 参数糖</a></h5>

<h5><a href="#2.4.5">2.4.5 你的糖中还有糖吗？</a></h5>

<h4><a href="#2.5">2.5 作用域的路由规则</a></h4>

<h5><a href="#2.5.1">2.5.1 Controller</a></h5>

<h5><a href="#2.5.2">2.5.2 路径前缀</a></h5>

<h5><a href="#2.5.3">2.5.3 命名前缀</a></h5>

<h5><a href="#2.5.4">2.5.4 命名空间</a></h5>

<h5><a href="#2.5.5">2.5.5 捆绑约束</a></h5>

<h4><a href="#2.6">2.6 路由列表</a></h4>

<h2 id='2.1'>2.1 路由的两个目标</h2>


<p>路由系统做两件事：</p>

<ol>
<li><p>通过请求匹配对应的controller的action方法</p></li>
<li><p>为你的方法（像link_to  redirect_to）动态生成URL</p></li>
</ol>


<p>路由定义了一个规则，用来作为匹配URL的模板和作为创建url的蓝图，这种规则会按照惯例自动生成（例如REST资源）。这种规则包括静态子字符串和斜杠（模仿URL的写法），和作为与url的值相符合的位置(segment key)段参数的key。</p>

<p>一个路由包括一个或多个硬编码的段参数key形成键值对，然后通过params方法进入对应的controller的action中。键（:controller和:action）决定哪个controller的哪个action被调用。路由中的其他键值对的定义得到了参考。</p>

<p>来看一个例子：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;recipes/:ingredient&#39;</span> <span class="o">=&gt;</span> <span class="s2">&quot;recipes#index&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<p>在这个例子中，你可以找到：</p>

<ul>
<li><p>静态字符串（recipes）</p></li>
<li><p>斜杠（/）</p></li>
<li><p>段参数key（:ingredient）</p></li>
<li><p>controller和action的映射（recipes#index）</p></li>
<li><p>HTTP动词抑制方法（get）</p></li>
</ul>


<p>路由有许多丰富的语法，但不是意味着这个是最复杂的，也不是最简单的；由于实在是太多了，一个简单的路由，想这个例子，必须<strong>提供足够的信息去匹配现存的url</strong>并且<strong>可以生成新的url</strong>，路由语法的设计就是来解决这两个过程的。</p>

<br />




<h2 id="2.2">2.2 routes.rb文件</h2>


<hr />

<p>路由定义在config/routes.rb文件中，根据 Listing2.1 这个文件创建于你创建你的Rails应用时并且还有命令教你如何使用，</p>

<h6>Listing 2.1: The default routes.rb file</h6>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
<span class='line-number'>30</span>
<span class='line-number'>31</span>
<span class='line-number'>32</span>
<span class='line-number'>33</span>
<span class='line-number'>34</span>
<span class='line-number'>35</span>
<span class='line-number'>36</span>
<span class='line-number'>37</span>
<span class='line-number'>38</span>
<span class='line-number'>39</span>
<span class='line-number'>40</span>
<span class='line-number'>41</span>
<span class='line-number'>42</span>
<span class='line-number'>43</span>
<span class='line-number'>44</span>
<span class='line-number'>45</span>
<span class='line-number'>46</span>
<span class='line-number'>47</span>
<span class='line-number'>48</span>
<span class='line-number'>49</span>
<span class='line-number'>50</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="ss">Example</span><span class="p">:</span><span class="ss">:Application</span><span class="o">.</span><span class="n">routes</span><span class="o">.</span><span class="n">draw</span> <span class="k">do</span>
</span><span class='line'>  <span class="c1"># The priority is based upon order of creation: first created -&gt; highest</span>
</span><span class='line'>  <span class="c1"># priority.</span>
</span><span class='line'>  <span class="c1"># See how all your routes lay out with &quot;rake routes&quot;.</span>
</span><span class='line'>  <span class="c1"># You can have the root of your site routed with &quot;root&quot;</span>
</span><span class='line'>  <span class="c1"># root to: &#39;welcome#index&#39;</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Example of regular route:</span>
</span><span class='line'>  <span class="c1">#   get &#39;products/:id&#39; =&gt; &#39;catalog#view&#39;</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Example of named route that can be invoked with</span>
</span><span class='line'>  <span class="c1"># purchase_url(id: product.id)</span>
</span><span class='line'>  <span class="c1">#  get &#39;products/:id/purchase&#39; =&gt; &#39;catalog#purchase&#39;, as: :purchase</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Example resource route (maps HTTP verbs to controller actions</span>
</span><span class='line'>  <span class="c1">#automatically):</span>
</span><span class='line'>  <span class="c1">#   resources :products</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Example resource route with options:</span>
</span><span class='line'>  <span class="c1"># resources :products do</span>
</span><span class='line'>  <span class="c1">#   member do</span>
</span><span class='line'>  <span class="c1">#     get &#39;short&#39;</span>
</span><span class='line'>  <span class="c1">#     post &#39;toggle&#39;</span>
</span><span class='line'>  <span class="c1">#   end</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1">#   collection do</span>
</span><span class='line'>  <span class="c1">#     get &#39;sold&#39;</span>
</span><span class='line'>  <span class="c1">#   end</span>
</span><span class='line'>  <span class="c1"># end</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Example resource route with sub-resources:</span>
</span><span class='line'>  <span class="c1">#   resources :products do</span>
</span><span class='line'>  <span class="c1">#       resources :comments, :sales</span>
</span><span class='line'>  <span class="c1">#       resource :seller</span>
</span><span class='line'>  <span class="c1">#   end</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Example resource route with more complex sub-resources:</span>
</span><span class='line'>  <span class="c1">#   resources :products do</span>
</span><span class='line'>  <span class="c1">#     resources :comments</span>
</span><span class='line'>  <span class="c1">#     resources :sales do</span>
</span><span class='line'>  <span class="c1">#        get &#39;recent&#39;, on: :collection</span>
</span><span class='line'>  <span class="c1">#     end</span>
</span><span class='line'>  <span class="c1">#   end</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Example resource route within a namespace:</span>
</span><span class='line'>  <span class="c1">#   namespace :admin do</span>
</span><span class='line'>  <span class="c1">#     # Directs /admin/products/* to Admin::ProductsController</span>
</span><span class='line'>  <span class="c1">#     # (app/controllers/admin/products_controller.rb)</span>
</span><span class='line'>  <span class="c1">#     resources :products</span>
</span><span class='line'>  <span class="c1">#   end</span>
</span></code></pre></td></tr></table></div></figure>


<p>这个文件由Example::Application.routes 的draw 方法调用构成的，方法用到一个块，从文件的第二行到倒数第二行都是块的内容，
在运行时，块在ActionDispatch::Routing::Mapper实例中估值，你可以通过它设置整个路由系统。</p>

<p>路由系统不得不寻找一个匹配URL的模式，它尝试着辨识或匹配url产生的参数，按着定义的顺序执行；也就是，按照 routes.rb 里面的顺序。
如果所给的路由匹配失败，匹配历程将查找下一个再匹配，直到成功匹配，查询才结束。</p>

<br/>




<h3 id="2.2.1">2.2.1 路由规则</h3>


<hr />

<p>最基础的定义路由方法是提供URL的模式加上一个通过特殊参数:to 映射的controller类action方法。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;products/:id&#39;</span><span class="p">,</span> <span class="ss">to</span><span class="p">:</span> <span class="s1">&#39;products#show&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>这是比较通用的，提供一个简写形式：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;products/:id&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;products#show&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>David曾经公开评价过这种简写形式背后的设计决定，他说这是从2个来源汲取灵感的：</p>

<ol>
<li>因为我们一直在使用controller作为小写这种模式，而且在:controller => “main”的定义中也没有“Controller”这部分。</li>
<li>采用Ruby模式#表示你正在谈论一个实例方法，它的影响甚至被部分混合。Main#index会让你认为存在Main这个对象，然而没有；
每次输出MainController#index将会成为一个麻烦。也是同样地原因我们考虑过:controller => “main” 和 :controller => “MainController”。给了这些限制，我想“main#index”是迄今为止最好的选择。</li>
</ol>


<br/>




<h3 id="2.2.2">2.2.2 限制请求方法</h3>


<hr />

<p>Rails4，限制HTTP方法被用来操作路由。
如果你用match 命令去定义一个路由，你会通过via这个可选参数来完成：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">match</span> <span class="s1">&#39;products/:id&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;products#show&#39;</span><span class="p">,</span> <span class="ss">via</span><span class="p">:</span> <span class="ss">:get</span>
</span></code></pre></td></tr></table></div></figure>


<p>Rails提供更简洁的方法去表达这种限制，通过设计好的http方法来替换原来的match命令：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;products/:id&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;products#show&#39;</span>
</span><span class='line'><span class="n">post</span><span class="s1">&#39; products&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;products#create&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>如果，处于某些原因，你想使用多个http方法限制路由，可以通过将这些动词方法构造成数组，然后传递给:via即可：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">match</span> <span class="s1">&#39;products/:id&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;products#show&#39;</span><span class="p">,</span> <span class="ss">via</span><span class="p">:</span> <span class="o">[</span><span class="ss">:get</span><span class="p">,</span><span class="ss">:post</span><span class="o">]</span>
</span></code></pre></td></tr></table></div></figure>


<p>定义一个路由没有定义他的http方法，将会使Rails抛出RuntimeError 异常。
然而这里不作为推荐，一个路由仍然可以匹配任何的http方法，只要传递:any到:via即可</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">match</span> <span class="s1">&#39;products&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;products#index&#39;</span><span class="p">,</span> <span class="ss">via</span><span class="p">:</span> <span class="ss">:any</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h3 id="2.2.3">2.2.3 URL 模式</h3>


<hr />

<p>请记住，模式字符串中不需要对应每个字段，段键(segment keys ：表示url字符串中得参数符号)；事实上每个连接都需要controller和action，举个例子，你可以写如下的路由：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s2">&quot;:id&quot;</span> <span class="o">=&gt;</span> <span class="s2">&quot;products#show&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<p>它将会被如下的URL辨别：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="ss">http</span><span class="p">:</span><span class="sr">//</span><span class="ss">localhost</span><span class="p">:</span><span class="mi">3000</span><span class="o">/</span><span class="mi">8</span>
</span></code></pre></td></tr></table></div></figure>


<p>这个路由系统将设置params[:id]为8（基于:id的段键位置与url中得8位置相匹配），并且它会执行product这个controller的show方法。当然，在视觉上看这个路由有点微小。另一方面，下面例子的路由包含静态字符串products/，在URL模式中：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">match</span> <span class="s1">&#39;products/:id&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;products#show&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>在这个字符串锚文本的识别过程中，任何左边不包含products/的URL将不符合此路由。</p>

<p>至于URL的产生，路由中的静态字符串将会简单地代替路由系统生成URL。URL生成器生成URL是使用路由的模式字符串作为蓝图的。模式字符串规定了子串products。</p>

<p>讲到这里，你心中应该了解到路由的这两种双重的意图了&mdash;识别/生成，这也是为什么之前强调了几次的目的。
这也有专门用来记住的两个原则：</p>

<ol>
<li><p>同样的规则决定了识别和生成。整个系统都是这样建立起来的，你不再需要去写规则。你每写一次规则，逻辑将在两个方向流动。</p></li>
<li><p>URL将由路由系统生成（link_to 等），url <a href="http://example.com/products/19201">http://example.com/products/19201</a> 的结果没有包含当用户遵循它时应该发生的一丝线索&mdash;除了它的路由规则。路由规则提供了必要的信息去触发controller和action。有些人看着URL但是不知道路由规则，将不知道url映射到哪个controller和action。</p></li>
</ol>


<br/>




<h3 id="2.2.4">2.2.4 段键</h3>


<hr />

<p>URL的模式字符串可以包含参数（用一个符号表示），并称为段键。
在下面的路由声明中，:id就是段键：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;products/:id&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;products#show&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>当这个路由去匹配url请求时，该模式的:id部分将作为匹配部分，并且挑选片段的值。
举个例子，下面这个url的:id的值将会是4：<a href="http://example.com/products/4">http://example.com/products/4</a></p>

<p>这个路由，当他匹配的时候，将会总是带着用户到product controller的show这个action方法，你不久将会看到基于片段匹配controller和action的技术。在单引号中得:id符号将是路由的段键（可以将它视为一种变量类型），它的工作就是被一个值锁上。</p>

<p>上面例子的意思是params[:id]的值将会被设置成4，你可以在product controller中的show方法中读取这个值。</p>

<p>当你需要生成一串url，你必须提供一个值能连接url中模式字符串的段键。一个最简单的理解（并且最原始）的方式是使用hash，像这样：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">link_to</span> <span class="s2">&quot;Products&quot;</span><span class="p">,</span>
</span><span class='line'>  <span class="ss">controller</span><span class="p">:</span> <span class="s2">&quot;products&quot;</span><span class="p">,</span>
</span><span class='line'>  <span class="ss">action</span><span class="p">:</span> <span class="s2">&quot;show&quot;</span><span class="p">,</span>
</span><span class='line'>  <span class="nb">id</span><span class="p">:</span> <span class="mi">1</span>
</span></code></pre></td></tr></table></div></figure>


<p>就像你知道的那样，它确实有像当今共同的生成路由的方法，名叫具名路由，在hash中明确地提供了controller和action。然而，现在我们是回顾路由的基本知识。</p>

<p>在上面的link_to中，我们提供了三个参数，其中两个将会匹配路由中得硬编码和段键；第三个，:id将会分配给url模式中相符合的段键值。</p>

<p>非常重要的是理解link_to不需要知道是否提供硬编码或是段值。只需要知道（或者希望）那三个值，绑定着那三个键，就能足够精确一个路由和模式字符串；因此，能够生成自动生成URL的蓝图。</p>

<h4>i:硬编码参数</h4>

<p>你总是有可能插入额外的硬编码参数到定义的路由的，尽管这个它对url的匹配无任何作用：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;products/special&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;products#show&#39;</span><span class="p">,</span> <span class="ss">special</span><span class="p">:</span> <span class="s1">&#39;true&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>提醒你，我不支持上述这个例子的做法；对我来说（从风格问题上讲）指出不同的action，而不是插入一个分句，</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;products/special&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;products#special&#39;</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h3 id="2.2.5">2.2.5 聚焦于id字段</h3>


<hr />

<p>注意，对待URL中的:id字段并不是魔法，它只是一个当做一个值的名字对待而已。如果你想要，可以改变Rails的规则，例如将:id改为:blah，但是你也不得不在你的controller中得action像下面这样做：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="vi">@product</span><span class="o">=</span><span class="no">Product</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="n">params</span><span class="o">[</span><span class="ss">:blah</span><span class="o">]</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>:id这个字段仅仅是一个惯例，它映射了一个action的普遍行为，就是操作一条特定的数据库记录。路由主要的工作是确定controller和对应的action被执行。通过:id的hash，你去数据库获取想要的记录：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">class</span> <span class="nc">ProductsController</span> <span class="o">&lt;</span> <span class="no">ApplicationController</span>
</span><span class='line'>  <span class="k">def</span> <span class="nf">show</span>
</span><span class='line'>    <span class="vi">@product</span> <span class="o">=</span> <span class="no">Product</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="n">params</span><span class="o">[</span><span class="ss">:id</span><span class="o">]</span><span class="p">)</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h3 id="2.2.6">2.2.6 可选的段键</h3>


<hr />

<p>Rails3 引入定义URL可选部分的模式，最简单的阐述这种方法的方式是看下面例子，这是从旧版本的config/routes.rb 文件底部的例子：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">match</span> <span class="s1">&#39;:controller(/:action(/:id(.:format)))&#39;</span><span class="p">,</span> <span class="ss">via</span><span class="p">:</span> <span class="ss">:any</span>
</span></code></pre></td></tr></table></div></figure>


<p>注意圆括号是用来定义可选段键的，有点像正则表达式中的可选组合。</p>

<br/>




<h3 id="2.2.7">2.2.7 重定向路由</h3>


<hr />

<p>你可以在直接在路由定义中直接编写一个redirect重定向，只要使用redirect方法：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s2">&quot;/foo&quot;</span><span class="p">,</span> <span class="ss">to</span><span class="p">:</span> <span class="n">redirect</span><span class="p">(</span><span class="s1">&#39;/bar&#39;</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>redirect的参数url可以是一个相对地址也可以是一个绝对地址。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s2">&quot;/google&quot;</span><span class="p">,</span><span class="ss">to</span><span class="p">:</span> <span class="n">redirect</span><span class="p">(</span><span class="s1">&#39;http://google.com/&#39;</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>redirect方法可以使用一个块，接收params请求作为他的参数；举个例子，做一个web服务端api的快速版本：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">match</span><span class="s2">&quot;/api/v1/:api&quot;</span><span class="p">,</span><span class="ss">to</span><span class="p">:</span>
</span><span class='line'>    <span class="n">redirect</span> <span class="p">{</span><span class="o">|</span><span class="n">params</span><span class="o">|</span> <span class="s2">&quot;/api/v2/</span><span class="si">#{</span><span class="n">params</span><span class="o">[</span><span class="ss">:api</span><span class="o">].</span><span class="n">pluralize</span><span class="si">}</span><span class="s2">&quot;</span> <span class="p">},</span> <span class="ss">via</span><span class="p">:</span> <span class="ss">:any</span>
</span></code></pre></td></tr></table></div></figure>


<p>redirect也接受:status参数：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">match</span> <span class="s2">&quot;/api/v1/:api&quot;</span><span class="p">,</span> <span class="ss">:to</span><span class="o">=&gt;</span>
</span><span class='line'>  <span class="n">redirect</span><span class="p">(</span><span class="ss">status</span><span class="p">:</span> <span class="mi">302</span><span class="p">)</span> <span class="p">{</span><span class="o">|</span><span class="n">params</span><span class="o">|</span> <span class="s2">&quot;/api/v2/</span><span class="si">#{</span><span class="n">params</span><span class="o">[</span><span class="ss">:api</span><span class="o">].</span><span class="n">pluralize</span><span class="si">}</span><span class="s2">&quot;</span> <span class="p">},</span> <span class="ss">via</span><span class="p">:</span> <span class="ss">:any</span>
</span></code></pre></td></tr></table></div></figure>


<p>redirect 返回的是ActionDispatch::Routing::Redirect的实例，看一下它的源代码：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
<span class='line-number'>30</span>
<span class='line-number'>31</span>
<span class='line-number'>32</span>
<span class='line-number'>33</span>
<span class='line-number'>34</span>
<span class='line-number'>35</span>
<span class='line-number'>36</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">module</span> <span class="nn">ActionDispatch</span>
</span><span class='line'>  <span class="k">module</span> <span class="nn">Routing</span>
</span><span class='line'>    <span class="k">class</span> <span class="n">redirect</span>
</span><span class='line'>      <span class="c1"># :nodoc: ...</span>
</span><span class='line'>      <span class="k">def</span> <span class="nf">call</span><span class="p">(</span><span class="n">env</span><span class="p">)</span>
</span><span class='line'>        <span class="n">req</span> <span class="o">=</span> <span class="no">Request</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="n">env</span><span class="p">)</span>
</span><span class='line'>
</span><span class='line'>        <span class="c1"># If any of the path parameters has a invalid encoding then </span>
</span><span class='line'>        <span class="c1"># raise since it&#39;s likely to trigger errors further on.</span>
</span><span class='line'>
</span><span class='line'>        <span class="n">req</span><span class="o">.</span><span class="n">symbolized_path_parameters</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">key</span><span class="p">,</span> <span class="n">value</span><span class="o">|</span>
</span><span class='line'>          <span class="k">unless</span> <span class="n">value</span><span class="o">.</span><span class="n">valid_encoding?</span>
</span><span class='line'>          <span class="k">raise</span> <span class="ss">ActionController</span><span class="p">:</span><span class="ss">:BadRequest</span><span class="p">,</span>
</span><span class='line'>          <span class="s2">&quot;Invalid parameter: </span><span class="si">#{</span><span class="n">key</span><span class="si">}</span><span class="s2"> =&gt; </span><span class="si">#{</span><span class="n">value</span><span class="si">}</span><span class="s2">&quot;</span>
</span><span class='line'>        <span class="k">end</span>
</span><span class='line'>      <span class="k">end</span>
</span><span class='line'>
</span><span class='line'>      <span class="n">uri</span> <span class="o">=</span> <span class="no">URI</span><span class="o">.</span><span class="n">parse</span><span class="p">(</span><span class="n">path</span><span class="p">(</span><span class="n">req</span><span class="o">.</span><span class="n">symbolized_path_parameters</span><span class="p">,</span> <span class="n">req</span><span class="p">))</span> <span class="n">uri</span><span class="o">.</span><span class="n">scheme</span> <span class="o">||=</span> <span class="n">req</span><span class="o">.</span><span class="n">scheme</span>
</span><span class='line'>      <span class="n">uri</span><span class="o">.</span><span class="n">host</span> <span class="o">||=</span> <span class="n">req</span><span class="o">.</span><span class="n">host</span>
</span><span class='line'>      <span class="n">uri</span><span class="o">.</span><span class="n">port</span> <span class="o">||=</span> <span class="n">req</span><span class="o">.</span><span class="n">port</span> <span class="k">unless</span> <span class="n">req</span><span class="o">.</span><span class="n">standard_port?</span>
</span><span class='line'>
</span><span class='line'>      <span class="n">body</span> <span class="o">=</span> <span class="sx">%(&lt;html&gt;&lt;body&gt;You are being &lt;a href=&quot;</span><span class="si">#{</span><span class="ss">ERB</span><span class="p">:</span><span class="ss">:Util</span><span class="o">.</span><span class="n">h</span><span class="p">(</span><span class="n">uri</span><span class="o">.</span><span class="n">to_s</span><span class="p">)\</span> <span class="si">}</span><span class="sx">&quot;&gt;redirected&lt;/a&gt;.&lt;/body&gt;&lt;/html&gt;)</span>
</span><span class='line'>
</span><span class='line'>      <span class="n">headers</span> <span class="o">=</span> <span class="p">{</span>
</span><span class='line'>              <span class="s1">&#39;Location&#39;</span> <span class="o">=&gt;</span> <span class="n">uri</span><span class="o">.</span><span class="n">to_s</span><span class="p">,</span>
</span><span class='line'>              <span class="s1">&#39;Content-Type&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;text/html&#39;</span><span class="p">,</span>
</span><span class='line'>              <span class="s1">&#39;Content-Length&#39;</span> <span class="o">=&gt;</span> <span class="n">body</span><span class="o">.</span><span class="n">length</span><span class="o">.</span><span class="n">to_s</span>
</span><span class='line'>      <span class="p">}</span>
</span><span class='line'>
</span><span class='line'>      <span class="o">[</span><span class="n">status</span><span class="p">,</span> <span class="n">headers</span><span class="p">,</span> <span class="o">[</span><span class="n">body</span><span class="o">]</span> <span class="o">]</span>
</span><span class='line'>
</span><span class='line'>      <span class="k">end</span>
</span><span class='line'>      <span class="o">.</span><span class="n">.</span><span class="o">.</span>
</span><span class='line'>    <span class="k">end</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h3 id="2.2.8">2.2.8 格式段format</h3>


<hr />

<p>我们来重新访问之前的默认路由：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">match</span> <span class="s1">&#39;:controller(/:action(/:id(.:format)))&#39;</span><span class="p">,</span> <span class="ss">via</span><span class="p">:</span> <span class="ss">:any</span>
</span></code></pre></td></tr></table></div></figure>


<p>.:format将匹配id字段后面.之后的值，举个例子，像如下的url：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="ss">http</span><span class="p">:</span><span class="sr">//</span><span class="ss">localhost</span><span class="p">:</span><span class="mi">3000</span><span class="o">/</span><span class="n">products</span><span class="o">/</span><span class="n">show</span><span class="o">/</span><span class="mi">3</span><span class="o">.</span><span class="n">json</span>
</span></code></pre></td></tr></table></div></figure>


<p>在这里，params[:format]将会被设置成为json。:format很特别，它在controller的action中有一个作用，这个作用与调用respond_to方法有关。</p>

<p>respond_to方法允许你的action依据请求的格式返回不同的结果，这里的product_controller的show方法提供了html和json两种格式：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">def</span> <span class="nf">show</span>
</span><span class='line'>  <span class="vi">@product</span> <span class="o">=</span> <span class="no">Product</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="n">params</span><span class="o">[</span><span class="ss">:id</span><span class="o">]</span><span class="p">)</span>
</span><span class='line'>  <span class="n">respond_to</span> <span class="k">do</span> <span class="o">|</span><span class="nb">format</span><span class="o">|</span>
</span><span class='line'>    <span class="nb">format</span><span class="o">.</span><span class="n">html</span>
</span><span class='line'>    <span class="nb">format</span><span class="o">.</span><span class="n">json</span> <span class="p">{</span> <span class="n">render</span> <span class="ss">json</span><span class="p">:</span> <span class="vi">@product</span><span class="o">.</span><span class="n">to_json</span>  <span class="p">}</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>这个respond_to的块中有两个分句，html分句是由format.html组成，对于html格式的请求将采用正常渲染方式，而json分句包含一个代码块；如果json被请求，那么json中的代码块将会被执行，并且其结果将会返回到客户端。</p>

<p>这里有个使用curl命令的结果：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'>curl http://localhost:3000/products/show/1.json -i
</span><span class='line'>HTTP/1.1 200 OK
</span><span class='line'>Content-Type: application/json; <span class="nv">charset</span><span class="o">=</span>utf-8
</span><span class='line'>Content-Length:81
</span><span class='line'>Connection:Keep-Alive
</span><span class='line'>
</span><span class='line'><span class="o">{</span><span class="s2">&quot;created_at&quot;</span>:<span class="s2">&quot;2013-02-09T18:25:03.513Z&quot;</span>,
</span><span class='line'> <span class="s2">&quot;description&quot;</span>:<span class="s2">&quot;Keyboard&quot;</span>,
</span><span class='line'> <span class="s2">&quot;id&quot;</span>:<span class="s2">&quot;1&quot;</span>,
</span><span class='line'> <span class="s2">&quot;maker&quot;</span>:<span class="s2">&quot;Apple&quot;</span>,
</span><span class='line'> <span class="s2">&quot;updated_at&quot;</span>:<span class="s2">&quot;2013-02-09T18:25:03.513Z&quot;</span><span class="o">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>URL最后以.json结尾会导致respond_to选择json分支，并且返回json表达的结果。</p>

<p>如果请求的格式不包含在respond_to的块里面，rails不会抛出异常，Rails会返回406 Not Acceptable status，告诉你无法处理这种请求。</p>

<p>如果你想要在respond_to的块里设置其他情况的处理，你可以使用any方法，这将会告诉rails处理那些没有被清晰定义的其他请求格式。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">def</span> <span class="nf">show</span>
</span><span class='line'>  <span class="vi">@product</span> <span class="o">=</span> <span class="no">Product</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="n">params</span><span class="o">[</span><span class="ss">:id</span><span class="o">]</span><span class="p">)</span>
</span><span class='line'>  <span class="n">respond_to</span> <span class="k">do</span> <span class="o">|</span><span class="nb">format</span><span class="o">|</span>
</span><span class='line'>    <span class="nb">format</span><span class="o">.</span><span class="n">html</span>
</span><span class='line'>    <span class="nb">format</span><span class="o">.</span><span class="n">json</span> <span class="p">{</span> <span class="n">render</span> <span class="ss">json</span><span class="p">:</span> <span class="vi">@product</span><span class="o">.</span><span class="n">to_json</span>  <span class="p">}</span>
</span><span class='line'>    <span class="nb">format</span><span class="o">.</span><span class="n">any</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>你只要告诉any方法该如何处理那个格式的请求或者有那个对应格式的视图模板，否则你将会得到 MissingTemplate 异常。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'>ActionView::MissingTemplate<span class="o">(</span>Missingtemplateproducts/show, application/show with <span class="o">{</span>:locale<span class="o">=</span>&gt;<span class="o">[</span>:en<span class="o">]</span>, :formats<span class="o">=</span>&gt;<span class="o">[</span>:xml<span class="o">]</span>, :handlers<span class="o">=</span>&gt;<span class="o">[</span>:erb, :builder, :raw, :ruby, :jbuilder, :coffee<span class="o">]}</span>.<span class="o">)</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h3 id="2.2.9">2.2.9 路由作为Rack的端点</h3>


<hr />

<p>在这一章的路由中你会见到可选的参数:to的用法，最有意思的是:to的值将会作为指向Rack的端点(Rack Endpoint)，看看下面简单的例子：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s2">&quot;/hello&quot;</span><span class="p">,</span> <span class="ss">to</span><span class="p">:</span> <span class="nb">proc</span><span class="p">{</span><span class="o">|</span><span class="n">env</span><span class="o">|</span> <span class="o">[</span> <span class="mi">200</span><span class="p">,</span> <span class="p">{},</span> <span class="o">[</span><span class="s2">&quot;Helloworld&quot;</span><span class="o">]</span> <span class="o">]</span> <span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>路由到controllers是非常松耦合的！最简洁的语法是（像&#8221;items#show&#8221;）依靠controller类的action方法去返回执行action请求的Rack Endpoint。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="o">&gt;&gt;</span> <span class="no">ItemsController</span><span class="o">.</span><span class="n">action</span><span class="p">(</span><span class="ss">:show</span><span class="p">)</span>
</span><span class='line'><span class="o">=&gt;</span> <span class="c1">#&lt;Proc:0x01e96cd0@...&gt;</span>
</span></code></pre></td></tr></table></div></figure>


<p>派发基于Rack应用的能力，像由Sinatra创建的app，可以实现使用amount方法。
amount方法接收一个:at可选项可以说明基于Rack的应用映射的路由。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">class</span> <span class="nc">HelloApp</span> <span class="o">&lt;</span> <span class="ss">Sinatra</span><span class="p">:</span><span class="ss">:Base</span>
</span><span class='line'>  <span class="n">get</span> <span class="s2">&quot;/&quot;</span> <span class="k">do</span>
</span><span class='line'>    <span class="s2">&quot;Hello World!&quot;</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="ss">Example</span><span class="p">:</span><span class="ss">:Application</span><span class="o">.</span><span class="n">routes</span><span class="o">.</span><span class="n">draw</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">mount</span> <span class="no">HelloApp</span><span class="p">,</span> <span class="ss">at</span><span class="p">:</span> <span class="s1">&#39;/hello&#39;</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>当然，更简洁的方式是：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">mount</span> <span class="no">HelloApp</span> <span class="o">=&gt;</span> <span class="s1">&#39;/hello&#39;</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h3 id="2.2.10">2.2.10 接收头</h3>


<hr />

<p>你可以通过设置请求的接收头（Accept Headers）来触发respond_to的其他分句，当你这样做了，就不需要在URL末尾加上.:format。（然而，由于http客户端的不一致，现实使用这种技术并不是很可靠）。</p>

<p>下面使用curl的例子，没有定义.json格式，但是不需要将接收头设置成application/json。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="vg">$curl</span> <span class="o">-</span><span class="n">i</span> <span class="o">-</span><span class="n">H</span> <span class="s2">&quot;Accept: application/json&quot;</span>
</span><span class='line'><span class="ss">http</span><span class="p">:</span><span class="sr">//</span><span class="ss">localhost</span><span class="p">:</span><span class="mi">3000</span><span class="o">/</span><span class="n">products</span><span class="o">/</span><span class="n">show</span><span class="o">/</span><span class="mi">1</span>
</span><span class='line'><span class="no">HTTP</span><span class="o">/</span><span class="mi">1</span><span class="o">.</span><span class="mi">1</span> <span class="mi">200</span> <span class="no">OK</span>
</span><span class='line'><span class="no">Content</span><span class="o">-</span><span class="ss">Type</span><span class="p">:</span> <span class="n">application</span><span class="o">/</span><span class="n">json</span><span class="p">;</span><span class="n">charset</span><span class="o">=</span><span class="n">utf</span><span class="o">-</span><span class="mi">8</span>
</span><span class='line'><span class="no">Content</span><span class="o">-</span><span class="ss">Length</span><span class="p">:</span> <span class="mi">81</span>
</span><span class='line'><span class="ss">Connection</span><span class="p">:</span> <span class="no">Keep</span><span class="o">-</span><span class="no">Alive</span>
</span><span class='line'>
</span><span class='line'><span class="p">{</span><span class="s2">&quot;created_at&quot;</span><span class="ss">:&quot;2013-02-09T18:25:03.513Z&quot;</span><span class="p">,</span>
</span><span class='line'>   <span class="s2">&quot;description&quot;</span><span class="ss">:&quot;Keyboard&quot;</span><span class="p">,</span>
</span><span class='line'>   <span class="s2">&quot;id&quot;</span><span class="ss">:&quot;1&quot;</span><span class="p">,</span>
</span><span class='line'>   <span class="s2">&quot;maker&quot;</span><span class="ss">:&quot;Apple&quot;</span><span class="p">,</span>
</span><span class='line'>   <span class="s2">&quot;updated_at&quot;</span><span class="ss">:&quot;2013-02-09T18:25:03.513Z&quot;</span><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h3 id="2.2.11">2.2.11 段键约束</h3>


<hr />

<p>有时候你不仅仅需要辨认一个路由，还需要辨别比现在更细粒度的组件或字段，你可以使用:constraint选项进行限制（可能需要正则表达式）。</p>

<p>举个例子，如果id为非数值，你可以路由许多show 请求到一个错误的action。你可以创建两个路由，一个处理id为数值的路由，另一个处理错误的路由。</p>

<h4>i:隐式锚文本</h4>

<blockquote><p>如果我们使用下面的限制：</p>

<p>constraints: {:id => /\d+/}</p>

<p>乍一看，好像会匹配&#8221;foo32bar&#8221;。其实不会，因为rails隐式锚文本会在表达式前后增加终结符。</p>

<p>事实上，像这样在表达式前后增加\A 和 \Z会导致Rails抛出异常。</p></blockquote>

<p>事实上，我们经常给:id增加限制，rails提供了更加简洁的方式：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;:controller/show/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:show</span><span class="p">,</span> <span class="nb">id</span><span class="p">:</span> <span class="sr">/\d+/</span>
</span><span class='line'><span class="n">get</span> <span class="s1">&#39;:controller/show/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:show_error</span>
</span></code></pre></td></tr></table></div></figure>


<p>正则表达式中的路由非常有用，特别是当你的路由中组件只是值不同时。但是，它们并不能作为数据完整性检查的替代品。你可能仍然需要确定你所处理的值是对于你的项目是有用或合适的。</p>

<p>从例子看，你可能总结为:constraints 检查params中的元素。然而，你也可以利用:constraints来检查任何一个请求“返回字符串的属性”，就像:subdomain和:referrer。对于匹配请求的方法，则不支持返回为数值或布尔型的，并且将会抛出神秘的异常。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># only allow users admin subdomain to do old-school routing</span>
</span><span class='line'><span class="n">get</span> <span class="s1">&#39;:controller/:action/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:show</span><span class="p">,</span> <span class="ss">constraints</span><span class="p">:</span> <span class="p">{</span><span class="ss">subdomain</span><span class="p">:</span> <span class="s1">&#39;admin&#39;</span><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>


<p>如果由于某些原因，你需要更加强大的限制性检查，有时候需要访问请求req，然后通过接受一个块或其他相应call的对象作为值来限制。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># protect records with id under 100</span>
</span><span class='line'> <span class="n">get</span><span class="s1">&#39;records/:id&#39;</span><span class="o">=&gt;</span><span class="s2">&quot;records#protected&quot;</span><span class="p">,</span>
</span><span class='line'> <span class="ss">constraints</span><span class="p">:</span> <span class="nb">proc</span> <span class="p">{</span><span class="o">|</span><span class="n">req</span><span class="o">|</span> <span class="n">req</span><span class="o">.</span><span class="n">params</span><span class="o">[</span><span class="ss">:id</span><span class="o">].</span><span class="n">to_i</span> <span class="o">&lt;</span> <span class="mi">100</span> <span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h3 id="2.2.12">2.2.12 根路由</h3>


<hr />

<p>config/routes.rb文件的默认第8行，你会见到：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># You can have the root of your site routed with &quot;root&quot;</span>
</span><span class='line'><span class="c1"># root to: &#39;welcome#index&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>上述代码的作用是，当你的浏览器连接：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="ss">http</span><span class="p">:</span><span class="sr">//ex</span><span class="n">ample</span><span class="o">.</span><span class="n">com</span> <span class="c1"># Note the lack of &quot;/anything&quot; at the end!</span>
</span></code></pre></td></tr></table></div></figure>


<p>路由会说：“我不需要任何值，我不需要任何东西，我已经知道是哪个controller的哪个action了，我现在就去触发它。”</p>

<p>在一个最新创建的路由中，这一行是被注释掉的，因为并不是默认需要到的。你需要确定你写的应用URL不应该做什么。
下面是简单的对于空路由的例子：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">root</span> <span class="ss">:to</span> <span class="o">=&gt;</span> <span class="s2">&quot;welcome#index&quot;</span>
</span><span class='line'><span class="n">root</span> <span class="ss">:to</span> <span class="o">=&gt;</span> <span class="s2">&quot;pages#home&quot;</span>
</span><span class='line'>
</span><span class='line'><span class="c1">#Shorthand syntax</span>
</span><span class='line'><span class="n">root</span> <span class="s2">&quot;user_sessions#new&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<p>定义空路由给那些只用域名的url连接你的站点的用户有东西可以看。</p>

<p>当你没有建立根路由，默认Rails会连接到因特网controller为Rails::WelcomeController 的页面。</p>

<p>在之前rails版本中，新创建的Rails项目通过引入public/目录下地index.html文件都把这些自动完成了。所有public/目录下的静态文本的层次结构将匹配你的应用中提出的URL方案，结果导致静态内容被服务而不是触发路由规则。
事实上，Web服务器会服务这些静态内容而而不需要Rails参与。</p>

<h3>注意路由顺序：</h3>

<blockquote><p>路由都是为了“辨别”和“产生”而按顺序排列在config/routes.rb文件中。</p></blockquote>

<br/>




<h2 id="2.3">2.3 路径匹配</h2>


<p>在某些情况下，你可能需要抓取一个或更多的路由组件并且不需要一个个匹配它们的位置参数。举个例子，你的URL可能映射成一个目录结构。如果有人连接：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'>/items/list/base/books/fiction/dickens
</span></code></pre></td></tr></table></div></figure>


<p>你想通过items/list这action访问剩下的三个字段，但是，有时可能仅有三个字段：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'>/items/list/base/books/fiction
</span></code></pre></td></tr></table></div></figure>


<p>或者5个：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'>/items/list/base/books/fiction/dickens/little_dorrit
</span></code></pre></td></tr></table></div></figure>


<p>所以，在特殊情况下，你需要一个路由去匹配URI的第二个组件后面的所有东西，你可以通过星号通配符进行路径匹配。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;items/list/*specs&#39;</span><span class="p">,</span><span class="ss">controller</span><span class="p">:</span> <span class="s1">&#39;items&#39;</span><span class="p">,</span> <span class="ss">action</span><span class="p">:</span> <span class="s1">&#39;list&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>现在items/list这个action可以访问一串不同数量的以/分开字段的URL了，可以通过params[:specs]访问：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">def</span> <span class="nf">list</span>
</span><span class='line'> <span class="n">specs</span> <span class="o">=</span> <span class="n">params</span><span class="o">[</span><span class="ss">:specs</span><span class="o">]</span> <span class="c1"># e.g, &quot;base/books/fiction/dickens&quot;</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<h3>匹配键值对</h3>

<blockquote><p>路径匹配应该对字段的临时查询提供一个普遍的机制基础。如果让你通过下面形式设计的URI方案：</p>

<p><a href="http://localhost:3000/items/q/field1/value1/field2/value2/...">http://localhost:3000/items/q/field1/value1/field2/value2/&#8230;</a></p>

<p>用这种方法发出的请求会返回一连串所有匹配每个字段的产品。</p>

<p>换句话说， <a href="http://localhost:3000/items/q/year/1939/material/wood">http://localhost:3000/items/q/year/1939/material/wood</a> 会产生一系列在1993年生产的木材。完成这个路由将是这个样子：</p></blockquote>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;items/q/*specs&#39;</span><span class="p">,</span> <span class="ss">controller</span><span class="p">:</span> <span class="s2">&quot;items&quot;</span><span class="p">,</span> <span class="ss">action</span><span class="p">:</span> <span class="s2">&quot;query&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<blockquote><p>当然，你将不得不像这样去写action查询：</p></blockquote>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">def</span> <span class="nf">query</span>
</span><span class='line'>  <span class="vi">@items</span> <span class="o">=</span> <span class="no">Item</span><span class="o">.</span><span class="n">where</span><span class="p">(</span><span class="no">Hash</span><span class="o">[</span><span class="n">params</span><span class="o">[</span><span class="ss">:specs</span><span class="o">].</span><span class="n">split</span><span class="p">(</span><span class="s2">&quot;/&quot;</span><span class="p">)</span><span class="o">]</span><span class="p">)</span>
</span><span class='line'>  <span class="k">if</span> <span class="vi">@items</span><span class="o">.</span><span class="n">empty?</span>
</span><span class='line'>    <span class="n">flash</span><span class="o">[</span><span class="ss">:error</span><span class="o">]</span> <span class="o">=</span> <span class="s2">&quot;Can&#39;t find items with those properties&quot;</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'>  <span class="n">render</span> <span class="ss">:index</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>Hash的类方法中括号是几个意思啊？他将一维数组转化成键值对hash！进一步证明，深入了解ruby是一个先决条件，让你成为一个专业的rails开发者。</p>

<br/>




<h2 id="2.4">2.4 命名路由</h2>


<p>事实上，你在这里学习的东西将直接进入我们在第3章中的相关路由的检查中。</p>

<p>命名路由这个方法是为了让作为程序员的你的生活更加简单，就应用程序而言，没有什么表面上看得见的效果。当你命名一个路由，一个新的方法将被定义并且在你的controller和view中使用，这个方法叫做name_url（name是你给路由的name），并且调用这个方法，使用合理的参数使路由产生相应的URL。</p>

<p>另外，有一个方法叫做name_path也会被创建，它会产生URL中没有协议和host的部分。</p>

<br/>




<h3 id="2.4.1">2.4.1 创建一个命名路由</h3>


<hr />

<p>为路由命名的方法是在路由规则中使用:as参数：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;help&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;help#index&#39;</span><span class="p">,</span> <span class="ss">as</span><span class="p">:</span> <span class="s1">&#39;help&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>在这个例子中，你将可以得到两个方法：help_url和help_path，你可以在使用到url时用这两个方法：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">link_to</span> <span class="s2">&quot;Help&quot;</span><span class="p">,</span> <span class="n">help_path</span>
</span></code></pre></td></tr></table></div></figure>


<p>当然，对辨识和产生也有效，该模式字符串包括静态字符串组件“help”。因此，你看到超链接的路径是：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'>/help
</span></code></pre></td></tr></table></div></figure>


<p>当有人点击这个link，help controller的index方法将会被调用。</p>

<h3>Xavier 说：</h3>

<blockquote><p>你可以在 console 中直接使用app 对象测试命名路由：</p></blockquote>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'> <span class="o">&gt;&gt;</span> <span class="n">app</span><span class="o">.</span><span class="n">clients_path</span>
</span><span class='line'> <span class="o">=&gt;</span> <span class="s2">&quot;/clients&quot;</span>
</span><span class='line'>
</span><span class='line'> <span class="o">&gt;&gt;</span> <span class="n">app</span><span class="o">.</span><span class="n">clients_url</span>
</span><span class='line'> <span class="o">=&gt;</span> <span class="s2">&quot;http://www.example.com/clients&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<p>命名路由给你省下很多生成路由的功夫，虽然如此，但是你还是需要为你的路由模式字符串任何段键提供相对应的值。</p>

<br/>




<h3 id="2.4.2"> 2.4.2 name_path vs name_url</h3>


<hr />

<p>当你创建一个命名路由，你几乎就是创建了两个helper方法，在之前的例子中，那两个路由方法分别是helper_path 和 helper_url，不同的是helper_url产生的是整个url，包括域名和协议。然而，_path产生的仅仅是路径部分。（有时候作为绝对路径或相对路径）</p>

<p>根据HTTP规范，重定向可以定义一个可以被编译的URI，这意味着它是一个完全合格的网址。因此，如果你想要坚持严谨，当你使用命名路由作为redirect_to的参数时，你可能需要总是运用_url版本。</p>

<p>其实redirect_to可以完美支持命名路由helper方法<em>path生成的相对路径。事实上，除了重定向(redirect)，还有永久链接（permalink）和一些其他情况，Rails都建议用</em>path代替_url方法，每当你这么做，基于HTTP头部请求、document的一个元素或是URL，他都会产生较短的字符串和用户代理（浏览器或其他的东西）可以推断出完全合格的URL。</p>

<p>如果你在练习这篇文章的代码之时，你可能会发现基本上<em>url和</em>path没什么区别。但是，我更倾向于在一般讨论中使用<em>url这种风格，而在view中使用</em>path风格（例如link_to或form_for）。这基本是书写风格方面的问题。使用<em>url更普遍，使用</em>path则更专业。</p>

<h3>使用字面的URL</h3>

<blockquote><p>如果你想要，你可以将路径或URL硬编码作为link_to或是redirect_to的字符串参数，举个例子：</p></blockquote>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">link_to</span> <span class="s2">&quot;Help&quot;</span><span class="p">,</span> <span class="ss">controller</span><span class="p">:</span> <span class="s2">&quot;main&quot;</span><span class="p">,</span> <span class="ss">action</span><span class="p">:</span> <span class="s2">&quot;help&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<blockquote><p>可以使用下面来替代：</p></blockquote>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">link_to</span> <span class="s2">&quot;Help&quot;</span><span class="p">,</span> <span class="s2">&quot;/main/help&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<blockquote><p>然而，在路由系统中使用字面路径或字面URL，你需要自己维护他（如果这是适合你做的方法，你当然可以使用Ruby的字符串插值技术插入值，但这真的符合Rails的两大原则吗？）</p></blockquote>

<br/>




<h3 id="2.4.3">2.4.3 给你的路由命名</h3>


<hr />

<p>最好的命名方法是按照REST的惯例，在另一个方面，你还需要自上而下的考虑，那就是，你需要在你的应用中写怎样的代码让创建路由成为可能。</p>

<p>举个例子，调用link_to:</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">link_to</span> <span class="s2">&quot;Auction of </span><span class="si">#{</span><span class="n">item</span><span class="o">.</span><span class="n">name</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">,</span>
</span><span class='line'>  <span class="ss">controller</span><span class="p">:</span> <span class="s2">&quot;items&quot;</span><span class="p">,</span>
</span><span class='line'>  <span class="ss">action</span><span class="p">:</span> <span class="s2">&quot;show&quot;</span><span class="p">,</span>
</span><span class='line'>  <span class="nb">id</span><span class="p">:</span> <span class="n">item</span><span class="o">.</span><span class="n">id</span>
</span></code></pre></td></tr></table></div></figure>


<p>这个路由规则匹配路径是（最普通的路由）</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s2">&quot;item/:id&quot;</span> <span class="o">=&gt;</span> <span class="s2">&quot;items#show&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<p>可以确定的是这样简短的路由会更加好看，毕竟，路由规则总是定义了controller和action。
下面这是item命名路由的很好的候选：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s2">&quot;item/:id&quot;</span> <span class="o">=&gt;</span> <span class="s2">&quot;items#show&quot;</span><span class="p">,</span> <span class="ss">as</span><span class="p">:</span> <span class="s2">&quot;item&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<p>通过在link_to中引入item_path来改善产生路由：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">link_to</span> <span class="s2">&quot;Auctionof</span><span class="si">#{</span><span class="n">item</span><span class="o">.</span><span class="n">name</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">,</span> <span class="n">item_path</span><span class="p">(</span><span class="nb">id</span><span class="p">:</span> <span class="n">item</span><span class="o">.</span><span class="n">id</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>给路由一个简短的命名，使我们省略一些查询路由的工作，提高效率，</p>

<br/>




<h3 id="2.4.4">2.4.4 参数糖</h3>


<hr />

<p>事实上，你给item_path的参数可以更短。如果你需要像命名路由提供一个id参数，完全可以直接将这个:id的值作为参数。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">link_to</span> <span class="s2">&quot;Auction of </span><span class="si">#{</span><span class="n">item</span><span class="o">.</span><span class="n">name</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">,</span> <span class="n">item_path</span><span class="p">(</span><span class="n">item</span><span class="o">.</span><span class="n">id</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>语法糖更加牛B：你可以传一个对象，Rails自动获取其中的id：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">link_to</span> <span class="s2">&quot;Auction of </span><span class="si">#{</span><span class="n">item</span><span class="o">.</span><span class="n">name</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">,</span> <span class="n">item_path</span><span class="p">(</span><span class="n">item</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>这些原则继承命名路由中模式字符串的其他段键，举个例子，如果你有一个路由像：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s2">&quot;auction/:auction_id/item/:id&quot;</span> <span class="o">=&gt;</span> <span class="s2">&quot;items#show&quot;</span><span class="p">,</span> <span class="ss">as</span><span class="p">:</span> <span class="s2">&quot;item&quot;</span>
</span></code></pre></td></tr></table></div></figure>


<p>你可以这样调用它：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">link_to</span> <span class="s2">&quot;Auction of </span><span class="si">#{</span><span class="n">item</span><span class="o">.</span><span class="n">name</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">,</span> <span class="n">item_path</span><span class="p">(</span><span class="n">auction</span><span class="p">,</span> <span class="n">item</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>然后你会得到像下面的路径：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'>/auction/5/item/11
</span></code></pre></td></tr></table></div></figure>


<p>在这里，我们让Rails自动推断auction和item的id值，它是通过你所传递给命名路由helper方法的参数（这个参数不管是否hash）调用to_param方法。只要你按照顺序给他们传递参数，就能获得对应的id值。</p>

<br/>




<h3 id="2.4.5">2.4.5 你的糖中还有糖吗？</h3>


<hr />

<p>而且，你不需要让Rails路由生成id值插入URL中，你可以通过在你的model中覆盖 to_param 方法来改变这个值。</p>

<p>假设你想要你的auction的item的描述信息出现在你的URL中。那么，在你的model中item.rb文件，请覆盖to_params方法；
在这里，我们覆盖它，让它提供一个“munged” （除去标点符号和加入连字符）。使用parameterize方法添加到Active Support的string中，它会使你的字符串转化成适合url的漂亮字符串。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">def</span> <span class="nf">to_param</span>
</span><span class='line'> <span class="n">description</span><span class="o">.</span><span class="n">parameterize</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>随后，调用item_path(auction, item)方法，将会产生如下内容：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'>/auction/3/item/cello-bow
</span></code></pre></td></tr></table></div></figure>


<p>当然，如果你在调用处区域用“cello-bow”代替id值，你将需要再次挖出对象。
博客应用利用这种技术创建slugs用来作为永久链接通常有一个单独字段来存储毁掉版本的部分路径的标题。
这样，我们可以这样做：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="no">Item</span><span class="o">.</span><span class="n">where</span><span class="p">(</span><span class="n">munged_description</span><span class="p">:</span> <span class="n">params</span><span class="o">[</span><span class="ss">:id</span><span class="o">]</span><span class="p">)</span><span class="o">.</span><span class="n">first!</span>
</span></code></pre></td></tr></table></div></figure>


<p>去查找正确的item记录。（没错，你可以在路由中调用id以外的其他东西使他更加清楚）</p>

<h3>Courtenay 说：</h3>

<blockquote><p>为什么在URL中不使用数字表示呢？</p>

<p>首先，你的竞争者可以通过url知道你创建了多少个auction。</p>

<p>连续数字的id也允许蜘蛛自动偷窃你的内容，成为进入你数据库的窗口。</p>

<p>使用文字使url更加好看。</p></blockquote>

<br/>




<h2 id="2.5">2.5 作用域的路由规则</h2>


<p>Rails提供各种方法给相关路由规则捆绑在一起。这都基于使用scope方法和它的各种快捷方式。打个比方，你想要给auctions添加如下路由：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">get</span> <span class="s1">&#39;auctions/new&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;auctions#new&#39;</span>
</span><span class='line'><span class="n">get</span> <span class="s1">&#39;auctions/edit/:id&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;auctions#edit&#39;</span>
</span><span class='line'><span class="n">post</span> <span class="s1">&#39;auctions/pause/:id&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;auctions#pause&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>你可以dry你的routes.rb文件，使用scope方法代替:</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">scope</span> <span class="ss">controller</span><span class="p">:</span> <span class="ss">:auctions</span> <span class="k">do</span>
</span><span class='line'>    <span class="n">get</span> <span class="s1">&#39;auctions/new&#39;</span> <span class="o">=&gt;</span> <span class="ss">:new</span>
</span><span class='line'>    <span class="n">get</span> <span class="s1">&#39;auctions/edit/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:edit</span>
</span><span class='line'>    <span class="n">post</span> <span class="s1">&#39;auctions/pause/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:pause</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>接着，你可以再次dry它，通过在scope方法添加:path参数：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">scope</span> <span class="ss">path</span><span class="p">:</span> <span class="s1">&#39;/auctions&#39;</span><span class="p">,</span> <span class="ss">controller</span><span class="p">:</span> <span class="ss">:auctions</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">get</span> <span class="s1">&#39;new&#39;</span> <span class="o">=&gt;</span> <span class="ss">:new</span>
</span><span class='line'>  <span class="n">get</span> <span class="s1">&#39;edit/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:edit</span>
</span><span class='line'>  <span class="n">post</span> <span class="s1">&#39;pause/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:pause</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h3 id="2.5.1">2.5.1 Controller</h3>


<hr />

<p>scope方法接收一个:controller项（或者可以理解为接收一个符号作为第一个参数并且会被假定为controller）。因此，下面两种定义方式是相同的：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">scope</span> <span class="ss">controller</span><span class="p">:</span> <span class="ss">:auctions</span> <span class="k">do</span>
</span><span class='line'><span class="n">scope</span> <span class="ss">:auctions</span> <span class="k">do</span>
</span></code></pre></td></tr></table></div></figure>


<p>为了使之更为明显，你可以使用controller方法替代scope方法，本质上也是一种语法糖：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">controller</span> <span class="ss">:auctions</span> <span class="k">do</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h3 id="2.5.2">2.5.2 路径前缀</h3>


<hr />

<p>scope方法接收一个:path选项进行限制（或者你可以理解为接收一字符串作为第一个参数并且会被作为路径的前缀），
因此，下面两种定义是相同的：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">scope</span> <span class="ss">path</span><span class="p">:</span> <span class="s1">&#39;/auctions&#39;</span> <span class="k">do</span>
</span><span class='line'><span class="n">scope</span> <span class="s1">&#39;/auctions&#39;</span> <span class="k">do</span>
</span></code></pre></td></tr></table></div></figure>


<p>Rails4有一个新功能，可以给:path传递符号代替原来的字符串作为参数，看下面定义：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">scope</span> <span class="ss">:auctions</span><span class="p">,</span> <span class="ss">:archived</span> <span class="k">do</span>
</span></code></pre></td></tr></table></div></figure>


<p>将scope下地所有路由嵌套在&#8221;/auctions/archived&#8221;路径下</p>

<br/>




<h3 id="2.5.3">2.5.3 命名前缀</h3>


<hr />

<p>scope方法也可以接收:as选项,它可以影响产生命名路由的helper方法。
例如，路由：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">scope</span> <span class="ss">:auctions</span><span class="p">,</span> <span class="ss">as</span><span class="p">:</span> <span class="s1">&#39;admin&#39;</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">get</span> <span class="s1">&#39;new&#39;</span> <span class="o">=&gt;</span> <span class="ss">:new</span><span class="p">,</span> <span class="ss">as</span><span class="p">:</span> <span class="s1">&#39;new_auction&#39;</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>将会产生URL的helper方法admin_new_auction_url.</p>

<br/>




<h3 id="2.5.4">2.5.4 命名空间</h3>


<hr />

<p>URL可以使用命名空间namespace方法进行分组，这是一个语法糖，被module包裹，将命名前缀和路径前缀设置为一个声明。
命名空间namespace方法将第一个参数转化为字符串，这就是为什么一些代码例子你会看到它接收一个符号：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">namespace</span> <span class="ss">:auctions</span><span class="p">,</span> <span class="ss">:controller</span> <span class="o">=&gt;</span> <span class="ss">:auctions</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">get</span> <span class="s1">&#39;new&#39;</span> <span class="o">=&gt;</span> <span class="ss">:new</span>
</span><span class='line'>  <span class="n">get</span> <span class="s1">&#39;edit/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:edit</span>
</span><span class='line'>  <span class="n">post</span> <span class="s1">&#39;pause/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:pause</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>




<br/>




<h3 id="2.5.5">2.5.5 捆绑约束</h3>


<hr />

<p>如果你发现你在相关的路由中重复写了一些相似的段键约束，你可以将它们捆绑在一起，然后在scope方法中使用:constraints选项</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">scope</span> <span class="ss">controller</span><span class="p">:</span> <span class="ss">:auctions</span><span class="p">,</span> <span class="ss">constraints</span><span class="p">:</span> <span class="p">{</span><span class="ss">:id</span><span class="o">=&gt;</span><span class="sr">/\d+/</span><span class="p">}</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">get</span> <span class="s1">&#39;edit/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:edit</span>
</span><span class='line'>  <span class="n">post</span> <span class="s1">&#39;pause/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:pause</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>它就像是给定的scope需要一个路由子规则来约束。事实上，如果你给一个没有接收段键值的规则加上约束，将会导致路由破坏。
既然你是嵌套的，你可能要使用的约束方法:constraints，它只是一种使规则定义更紧凑的语法糖。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">scope</span> <span class="ss">path</span><span class="p">:</span> <span class="s1">&#39;/auctions&#39;</span><span class="p">,</span> <span class="ss">controller</span><span class="p">:</span> <span class="ss">:auctions</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">get</span> <span class="s1">&#39;new&#39;</span> <span class="o">=&gt;</span> <span class="ss">:new</span>
</span><span class='line'>  <span class="n">constraints</span> <span class="nb">id</span><span class="p">:</span> <span class="sr">/\d+/</span> <span class="k">do</span>
</span><span class='line'>    <span class="n">get</span> <span class="s1">&#39;edit/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:edit</span>
</span><span class='line'>    <span class="n">post</span> <span class="s1">&#39;pause/:id&#39;</span> <span class="o">=&gt;</span> <span class="ss">:pause</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>为了重用模块化，你可以提供一个约束方法与有matches?方法的对象。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">class</span> <span class="nc">DateFormatConstraint</span>
</span><span class='line'>  <span class="k">def</span> <span class="nc">self</span><span class="o">.</span><span class="nf">matches?</span><span class="p">(</span><span class="n">request</span><span class="p">)</span>
</span><span class='line'>    <span class="n">request</span><span class="o">.</span><span class="n">params</span><span class="o">[</span><span class="ss">:date</span><span class="o">]</span> <span class="o">=~</span> <span class="sr">/\A\d{4}-\d\d-\d\d\z/</span> <span class="c1"># YYYY-MM-DD</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="c1"># inroutes.rb</span>
</span><span class='line'><span class="n">constraints</span><span class="p">(</span><span class="no">DateFormatConstraint</span><span class="p">)</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">get</span> <span class="s1">&#39;since/:date&#39;</span> <span class="o">=&gt;</span> <span class="ss">:since</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>在这个特殊的例子中（DateFormatConstraint），如果一个图谋不轨或怀有恶意的用户在URL中输入不好的格式的日期作为参数，Rails将会返回404状态码代替抛出异常。</p>

<br/>




<h2 id="2.6">2.6 路由列表</h2>


<p>一个好用的路由列表在Rails项目中被作为标准的rake任务使用，通过在你的应用目录下输入rake routes调用它。举个例子，这里输出一个routes文件包含仅仅一个resources :products规则：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="nv">$ </span>rake routes
</span><span class='line'>  products      GET   /products<span class="o">(</span>.:format<span class="o">)</span>            products#index
</span><span class='line'>                POST   /products<span class="o">(</span>.:format<span class="o">)</span>           products#create
</span><span class='line'>  new_product   GET    /products/new<span class="o">(</span>.:format<span class="o">)</span>       products#new
</span><span class='line'>  edit_product  GET    /products/:id/edit<span class="o">(</span>.:format<span class="o">)</span>  products#edit
</span><span class='line'>  product       GET    /products/:id<span class="o">(</span>.:format<span class="o">)</span>       products#show
</span><span class='line'>                PATCH  /products/:id<span class="o">(</span>.:format<span class="o">)</span>       products#update
</span><span class='line'>                PUT    /products/:id<span class="o">(</span>.:format<span class="o">)</span>       products#update
</span><span class='line'>                DELETE /products/:id<span class="o">(</span>.:format<span class="o">)</span>       products#destroy
</span></code></pre></td></tr></table></div></figure>


<p>输出分为四列，前两列是可选的并且包含路由名和http方法约束，当提供这两列的内容，第三列包含URL映射的字符串。最后，第四列指示路由应该映射哪个controller和哪个action，加上已经定义的路由段键约束。</p>

<p>注意路由任务可以选择一个controller作为环境来查找，看下面例子：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="nv">$ </span>rake routes <span class="nv">CONTROLLER</span><span class="o">=</span>products
</span></code></pre></td></tr></table></div></figure>


<p>这将会列出所有与ProductsController相关的路由。</p>

<br/>




<h2>总结</h2>


<p>上半篇帮助你全面了解Rails的普通路由规则和路由系统的两个怎样的目的。</p>

<ul>
<li><p>识别传入的请求并且映射到相应的controller和action，以及额外的变量。</p></li>
<li><p>识别URL参数方法（例如link_to）匹配相应路径，以便生成适当的HTML链接。</p></li>
</ul>


<p>我们通过在定义路由时使用一些先进的技术如正则表达式和通配符，还有在scope方法下捆绑共享相关路由来创立属于我们自己的路由。</p>

<p>最后，再继续进行之前，我们应该确保你理解如何命名路由工作，以及为什么它们让你变成更容易，让你的视图代码更加简洁。</p>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[Rails Enviroments and Configuration]]></title>
    <link href="https://TsaiKoga.github.com/blog/2015/07/25/rails-enviroments-and-configuration/"/>
    <updated>2015-07-25T13:03:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2015/07/25/rails-enviroments-and-configuration</id>
    <content type="html"><![CDATA[<p>对于 Rails 的环境和配置，这里翻译了一篇文章。如果有翻译错的地方，欢迎指出。</p>

<h2>目录：</h2>

<h4><a href="#1.1">1.1 Bunlder</a></h4>

<h5><a href="#1.1.1">1.1.1 Gemfile</a></h5>

<h6><a href="#1.1.1.1">1.1.1.1 直接从Git仓库加载 gems</a></h6>

<h6><a href="#1.1.1.2">1.1.1.2 从文件系统加载gem</a></h6>

<h5><a href="#1.1.2">1.1.2 安装Gem</a></h5>

<h5><a href="#1.1.3">1.1.3 Gem Locking</a></h5>

<h5><a href="#1.1.4">1.1.4 Gem Packages</a></h5>

<h4><a href="#1.2">1.2 启动和应用设置</a></h4>

<h5><a href="#1.2.1">1.2.1 application.rb</a></h5>

<h6><a href="#1.2.1.1">1.2.1.1 修改加载路径</a></h6>

<h6><a href="#1.2.1.2">1.2.1.2 Time Zones</a></h6>

<h6><a href="#1.2.1.3">1.2.1.3 Localization</a></h6>

<h6><a href="#1.2.1.4">1.2.1.4 Generator 的默认设置</a></h6>

<h5><a href="#1.2.2">1.2.2 Initializers</a></h5>

<h6><a href="#1.2.2.1">1.2.2.1 Backtrace Silencers</a></h6>

<h6><a href="#1.2.2.2">1.2.2.2 过滤参数日志</a></h6>

<h6><a href="#1.2.2.3">1.2.2.3 Inflections</a></h6>

<h6><a href="#1.2.2.4">1.2.2.4 自定义MIME Types</a></h6>

<h6><a href="#1.2.2.5">1.2.2.5 Secret Token</a></h6>

<h6><a href="#1.2.2.6">1.2.2.6 Session Store</a></h6>

<h6><a href="#1.2.2.7">1.2.2.7 参数包装</a></h6>

<h5><a href="#1.2.3">1.2.3 额外的配置</a></h5>

<h6><a href="#1.2.3.1">1.2.3.1 Log-Level覆盖</a></h6>

<h6><a href="#1.2.3.2">1.2.3.2 Schema Dumper</a></h6>

<h4><a href="#1.3">1.3 开发模式</a></h4>

<h5><a href="#1.3.1">1.3.1 自动加载类</a></h5>

<h5><a href="#1.3.2">1.3.2 Eager Load</a></h5>

<h5><a href="#1.3.3">1.3.3 错误报告</a></h5>

<h5><a href="#1.3.4">1.3.4 缓存</a></h5>

<h5><a href="#1.3.5">1.3.5 抛出发送错误</a></h5>

<h5><a href="#1.3.6">1.3.6 反对通知</a></h5>

<h5><a href="#1.3.7">1.3.7 慢查询的解释</a></h5>

<h5><a href="#1.3.8">1.3.8 待迁移错误页面</a></h5>

<h5><a href="#1.3.9">1.3.9 Assets的Debug模式</a></h5>

<h4><a href="#1.4">1.4 测试模式</a></h4>

<h4><a href="#1.5">1.5生产模式</a></h4>

<h5><a href="#1.5.1">1.5.1 Assets</a></h5>

<h4><a href="#1.6">1.6 日志</a></h4>

<h5><a href="#1.6.1">1.6.1 Rails的日志文件</a></h5>

<h5><a href="#1.6.2">1.6.2 标记日志</a></h5>

<h5><a href="#1.6.3">1.6.3 日志文件分析</a></h5>

<h6><a href="#1.6.3.1">1.6.3.1 Rails::Subscriber.colorize_logging</a></h6>

<h4><a href="#1.6.4">1.6.4 总结</a></h4>

<p>除了 RAILS_ENV 可以开启所需的环境，你也可以通过设置RACK_ENV 可以设置默认环境(development, production, test)</p>

<h2 id="1.1"> 1.1 Bundler</h2>


<p>Bundler 虽然不是Rails4 的特定工具，但是它却能够很好地解决你应用的gems依赖。
Bundler 通过一个配置文件Gemfile 中解决一些列版本的gems依赖。</p>

<h3 id="1.1.1"> 1.1.1 Gemfile</h3>


<hr />

<p>在你的Rails应用的根目录下，这个文件定义了你的Rails应用所有依赖，包括你所用的Rails 版本。Gemfile的基础语法很简单，如下：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">gem</span> <span class="s1">&#39;kaminari&#39;</span>
</span><span class='line'><span class="n">gem</span> <span class="s1">&#39;nokogiri&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>可以将这些gem依赖放在一个或多个环境中，具体做法是定义一个或多个环境符号的块，如下例子：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">group</span> <span class="ss">:development</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">gem</span> <span class="s1">&#39;pry-rails&#39;</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="n">group</span> <span class="ss">:test</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">gem</span> <span class="s1">&#39;capybara&#39;</span>
</span><span class='line'>  <span class="n">gem</span> <span class="s1">&#39;database_cleaner&#39;</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="n">group</span> <span class="ss">:development</span><span class="p">,</span> <span class="ss">:test</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">gem</span> <span class="s1">&#39;rspec-rails&#39;</span>
</span><span class='line'>  <span class="n">gem</span> <span class="s1">&#39;factory_girl_rails&#39;</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>


<p>这个gem 方法还接受第二个可选参数，也就是Rubygem的版本号，如果此参数为空，则会自动下载最新稳定的版本。
如何定义这第二个参数呢？看以下例子：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">gem</span> <span class="s1">&#39;nokogiri&#39;</span><span class="p">,</span> <span class="s1">&#39;1.5.6&#39;</span>
</span><span class='line'><span class="n">gem</span> <span class="s1">&#39;pry-rails&#39;</span><span class="p">,</span> <span class="s1">&#39;&gt; 0.2.2&#39;</span>
</span><span class='line'><span class="n">gem</span> <span class="s1">&#39;decent_exposure&#39;</span><span class="p">,</span> <span class="s1">&#39;~&gt;2.0.1&#39;</span>
</span><span class='line'><span class="n">gem</span> <span class="s1">&#39;draper&#39;</span><span class="p">,</span> <span class="s1">&#39;1.0.0.beta6&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>有些时候，你的gem需要用require语句加载进来，在这种情况下，你只需要在gem 的最右边声明就行了。
如：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">gem</span> <span class="s1">&#39;webmock&#39;</span><span class="p">,</span> <span class="nb">require</span><span class="p">:</span> <span class="s1">&#39;webmock/rspec&#39;</span>
</span></code></pre></td></tr></table></div></figure>




<h4 id="1.1.1.1"> 1.1.1.1 直接从Git仓库加载 gems</h4>


<hr />

<p>现在我们可以从<a href="https://rubygems.org">https://rubygems.org</a> 下载gems,也可以非常简单的从gem的仓库获取这个gem，如下代码：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">gem</span> <span class="s1">&#39;carrierwave&#39;</span><span class="p">,</span> <span class="ss">git</span><span class="p">:</span> <span class="s1">&#39;git@github.com:jnicklas/carrierwave.git&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>如果这个gem的源代码放在github上面，可以直接用:github ：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">gem</span> <span class="s1">&#39;carrierwave&#39;</span><span class="p">,</span> <span class="ss">github</span><span class="p">:</span><span class="s1">&#39;jnicklas/carrierwave&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>如果有几个gemspec共用一个git仓库，可以像如下代码操作:mZ    git &lsquo;git://github.com/rails/rails.git&rsquo;</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">gem</span> <span class="s1">&#39;railties&#39;</span>
</span><span class='line'><span class="n">gem</span> <span class="s1">&#39;action_pack&#39;</span>
</span><span class='line'><span class="n">gem</span> <span class="s1">&#39;active_model&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>另外，你可以通过gem的所属仓库，指定对应的ref，branch或者是tag：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">git</span> <span class="s1">&#39;git://github.com/rails/rails.git&#39;</span><span class="p">,</span> <span class="ss">ref</span><span class="p">:</span> <span class="s2">&quot;4aded&quot;</span>
</span><span class='line'><span class="n">git</span> <span class="s1">&#39;git://github.com/rails/rails.git&#39;</span><span class="p">,</span> <span class="ss">branch</span><span class="p">:</span> <span class="s1">&#39;3-2-stable&#39;</span>
</span><span class='line'><span class="n">git</span> <span class="s1">&#39;git://github.com/rails/rails.git&#39;</span><span class="p">,</span> <span class="ss">tag</span><span class="p">:</span> <span class="s1">&#39;v3.2.11&#39;</span>
</span><span class='line'>
</span><span class='line'><span class="n">gem</span> <span class="s1">&#39;nokogiri&#39;</span><span class="p">,</span> <span class="ss">git</span><span class="p">:</span> <span class="s1">&#39;git://github.com/tenderlove/nokogiri.git&#39;</span><span class="p">,</span> <span class="n">ref</span> <span class="o">=&gt;</span> <span class="s1">&#39;0eec4&#39;</span>
</span></code></pre></td></tr></table></div></figure>




<h4 id="1.1.1.2"> 1.1.1.2 从文件系统加载gem</h4>


<hr />

<p>有时候你在开发模式下，想要加载一个gem（例如你fork了一个gem，作了修改，但是没有提交，想测试一下）可以使用:path：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">gem</span> <span class="s1">&#39;nokogiri&#39;</span><span class="p">,</span> <span class="ss">path</span><span class="p">:</span> <span class="s1">&#39;~/code/nokogiri&#39;</span>
</span></code></pre></td></tr></table></div></figure>




<h3 id="1.1.2"> 1.1.2 安装Gem</h3>


<hr />

<p>当你对Gemfile做了修改，调用install命令确保Gemfile所有依赖都有效。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="nv">$ </span>bundle install
</span><span class='line'>Fetching gem metadata from https://rubygems.org/.........
</span><span class='line'>Fetching gem metadata from https://rubygems.org/.........
</span><span class='line'>Fetching git://github.com/rails/rails.git
</span><span class='line'>Fetching git://github.com/rails/activerecord-deprecated_finders.git
</span><span class='line'>Fetching git://github.com/rails/arel.git
</span><span class='line'>Fetching git://github.com/rails/coffee-rails.git
</span><span class='line'>Fetching git://github.com/rails/sprockets-rails.git
</span><span class='line'>Fetching git://github.com/rails/sass-rails.git
</span><span class='line'>Installing rake <span class="o">(</span>10.0.3<span class="o">)</span>
</span><span class='line'>Installing i18n <span class="o">(</span>0.6.1<span class="o">)</span>
</span><span class='line'>.........
</span></code></pre></td></tr></table></div></figure>


<p>install命令会更新所有你的Gemfile中不与其他依赖冲突的最新版本依赖。</p>

<h3 id="1.1.3"> 1.1.3 Gem Locking</h3>


<hr />

<p>每一次更新或安装Gem，Bundler都会计算你项目的gem依赖树，并将结果存储在Gemfile.lock文件中。所以，从这点看，在使用Gem时，Gemfile将会被锁定，Bundler只会加载特定的版本的Gem。</p>

<h3 id="1.1.4"> 1.1.4 Gem Packages</h3>


<hr />

<p>你可以将你所有的gems打包到vendor/cache目录中，使用如下命令：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>bundle Package
</span></code></pre></td></tr></table></div></figure>


<p>当运行bundle install时，将会直接使用vendor/cache目录中的gem而不连接<a href="https://rubygems.org">https://rubygems.org</a></p>

<p>注意：无Rails的脚本运行要加上bundle exec 来初始化，如：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>bundle <span class="nb">exec </span>guard
</span></code></pre></td></tr></table></div></figure>


<p>Bundler还可以为你所有的可执行bundle创建binstubs。通过调用bundle install带上参数&mdash;binstubs，就会在你的根目录下创建一个bin目录，其中包括一些RubyGems环境的可执行脚本：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1">#!/usr/bin/env ruby</span>
</span><span class='line'><span class="c1">#</span>
</span><span class='line'><span class="c1"># This file was generated by Bundler.</span>
</span><span class='line'><span class="c1">#</span>
</span><span class='line'><span class="c1"># The application &#39;guard&#39; is installed as part of a gem, and</span>
</span><span class='line'><span class="c1"># this file is here to facilitate running it.</span>
</span><span class='line'><span class="nb">require</span> <span class="s1">&#39;pathname&#39;</span>
</span><span class='line'><span class="no">ENV</span><span class="o">[</span><span class="s1">&#39;BUNDLE_GEMFILE&#39;</span><span class="o">]</span> <span class="o">||=</span> <span class="no">File</span><span class="o">.</span><span class="n">expand_path</span><span class="p">(</span><span class="s2">&quot;../../Gemfile&quot;</span><span class="p">,</span>
</span><span class='line'>                                           <span class="no">Pathname</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="bp">__FILE__</span><span class="p">)</span><span class="o">.</span><span class="n">realpath</span><span class="p">)</span>
</span><span class='line'><span class="n">mZ</span>    <span class="nb">require</span> <span class="s1">&#39;rubygems&#39;</span>
</span><span class='line'><span class="nb">require</span> <span class="s1">&#39;bundler/setup&#39;</span>
</span><span class='line'>
</span><span class='line'><span class="nb">load</span> <span class="no">Gem</span><span class="o">.</span><span class="n">bin_path</span><span class="p">(</span><span class="s1">&#39;guard&#39;</span><span class="p">,</span><span class="s1">&#39;guard&#39;</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>使用binstubs，可以不用加bundle exec 而直接从bin/目录执行脚本.</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="nv">$ </span>bin/guard
</span></code></pre></td></tr></table></div></figure>


<p>你还可以将./bin加入$PATH路径，然后就可以轻松的执行：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="nv">$ </span>guard
</span></code></pre></td></tr></table></div></figure>


<p>使用Rails4创建项目，会自动创建binstubs，创建了bin/bundle, bin/rails,bin/rake，更新特定的stubs，可以使用下列命令：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>rake rails:update:bin
</span></code></pre></td></tr></table></div></figure>




<h2 id="1.2"> 1.2 启动和应用设置</h2>


<hr />

<p>用Rails开启进程处理请求（例如：rails sever），第一件事就是加载config/boot.rb文件。
建立整个rails栈，主要引用三个文件：</p>

<blockquote><p>boot.rb: 建立bunlder和加载路径
application.rb: 加载rails的gems，为gems定义rails环境，进行应用配置
environments.rb:运行所有初始化</p></blockquote>

<h3 id="1.2.1"> 1.2.1 application.rb</h3>


<hr />

<p>config/application.rb是Rails应用设置的主要文件，也是config/environments.rb最先加载的文件。
让我们一步一步来看这个文件，application.rb的下一行，一旦config/boot.rb加载，轮子就转动</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="nb">require</span> <span class="no">File</span><span class="o">.</span><span class="n">expand_path</span><span class="p">(</span><span class="s1">&#39;../boot&#39;</span><span class="p">,</span><span class="bp">__FILE__</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>


<p>对于下面这行代码：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="nb">require</span> <span class="s1">&#39;rails/all&#39;</span>
</span></code></pre></td></tr></table></div></figure>


<p>这你可以更改，将你所想要的组件加载进来，而不是加载所有的rails组件。</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># To pick the frameworks you want, remove &#39;require &quot;rails/all&quot;&#39;</span>
</span><span class='line'><span class="c1"># and list the framework railties that you want:</span>
</span><span class='line'><span class="c1">#</span>
</span><span class='line'><span class="c1"># require &quot;active_model/railtie&quot;</span>
</span><span class='line'><span class="c1"># require &quot;active_record/railtie&quot;</span>
</span><span class='line'><span class="c1"># require &quot;action_controller/railtie&quot;</span>
</span><span class='line'><span class="c1"># require &quot;action_mailer/railtie&quot;</span>
</span><span class='line'><span class="c1"># require &quot;action_view/railtie&quot;</span>
</span><span class='line'><span class="c1"># require &quot;sprockets/railtie&quot;</span>
</span><span class='line'><span class="c1"># require &quot;rails/test_unit/railtie&quot;</span>
</span></code></pre></td></tr></table></div></figure>




<h4 id="1.2.1.1"> 1.2.1.1 修改加载路径</h4>


<hr />

<p>默认的rails会寻找标准目录如：app/models 或是app/controllers,自动作为加载路径，你也可以自己添加目录到加载路径：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Custom directories with classes and modules you want to be auto loadable</span>
</span><span class='line'><span class="c1">#config.autoload_paths += %W(#{config.root}/extras)</span>
</span></code></pre></td></tr></table></div></figure>


<p>注意：config.root指向你的rails应用的根目录，因此如果你需要，想要用一个presenters的目录代替原有的models，可以这么做：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">autoload_paths</span> <span class="o">+=</span> <span class="sx">%W(</span><span class="si">#{</span><span class="n">config</span><span class="o">.</span><span class="n">root</span><span class="si">}</span><span class="sx">/app/presenters)</span>
</span></code></pre></td></tr></table></div></figure>


<p>这里的%W方法作为以空白隔开元素的数组，使代码构建更加方便。</p>

<h4 id="1.2.1.2"> 1.2.1.2 Time Zones</h4>


<hr />

<p>rails4默认的time zones是utc，你也可以覆盖它的默认值：</p>

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Set Time.zone default to the specified zone and make activerecord</span>
</span><span class='line'><span class="c1"># auto-convert to this zone.</span>
</span><span class='line'><span class="c1"># Run &quot;rake-Dtime&quot; for a list of tasks for finding time zone names.</span>
</span><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">time_zone</span> <span class="o">=</span> <span class="s1">&#39;CentralTime(US&amp;Canada)&#39;</span>
</span></code></pre></td></tr></table></div></figure>




<p><h4 id="1.2.1.3"> 1.2.1.3 Localization</h3></p>

<hr />

<p>Rails默认的语言Locale是:en 英文，你也可以在配置文件进行修改：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># The default locale is :en and all translations from</span>
</span><span class='line'><span class="c1"># config/locales/<em>.rb,yml are auto loaded.</span>
</span><span class='line'><span class="c1"># config.i18n.load_path += Dir[Rails.root.join(&#39;my&#39;,&#39;locales&#39;,</span>
</span><span class='line'>                                             <span class="c1"># &#39;</em>.{rb,yml}&#39;)]</span>
</span><span class='line'><span class="c1"># config.i18n.default_locale = :de</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h4 id="1.2.1.4"> 1.2.1.4 Generator 的默认设置</h4></p>

<hr />

<p>generator脚本可以根据你的工具链做出特定假定；在这里设置确定的值可以减少命令行参数的输入。
例如：运用没有features的Rspec和haml作为模板引擎时，我们可以这么做：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Configure generators values. Many other options are available,</span>
</span><span class='line'><span class="c1"># be sure to check the documentation.</span>
</span><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">generators</span> <span class="k">do</span> <span class="o">|</span><span class="n">g</span><span class="o">|</span>
</span><span class='line'>  <span class="n">g</span><span class="o">.</span><span class="n">template_engine</span> <span class="ss">:haml</span>
</span><span class='line'>  <span class="n">g</span><span class="o">.</span><span class="n">test_framework</span> <span class="ss">:rspec</span><span class="p">,</span> <span class="ss">fixture</span><span class="p">:</span> <span class="kp">false</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>注意：rubygems的一些gems像rspec-rails,haml-rails,factory_gril_rails已经为你做了这些处理的。</p>

<p><h3 id="1.2.2"> 1.2.2 Initializers</h3></p>

<hr />

<p>Rails2介绍了一个概念，将配置设置放入config/initializers目录中建立的一个小的ruby文件，config/initializers目录中的文件会在程序启动后被自动加载。</p>

<p>你可以增加自己需要的配置设置，通过再initializers目录中建立ruby文件，很多人喜欢在这个目录中建立文件设置常量，为了安全这些常量的值放在yml文件中，通过initializers目录中的rb文件进行引入并赋予常量。</p>

<p><h4 id="1.2.2.1">1.2.2.1 Backtrace Silencers</h4></p>

<hr />

<p>没人喜欢很长的exception的回溯跟踪，rails 有个机制可以减少回溯的层数（这种方法是删除行）。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># You can add backtrace silencers for libraries that you&#39;re using but</span>
</span><span class='line'><span class="c1"># don&#39;t wish to see in your backtraces.</span>
</span><span class='line'><span class="no">Rails</span><span class="o">.</span><span class="n">backtrace_cleaner</span><span class="o">.</span><span class="n">add_silencer</span><span class="p">{</span><span class="o">|</span><span class="n">line</span><span class="o">|</span><span class="n">line</span><span class="o">=~</span><span class="sr">/my_noisy_library/</span><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="c1"># You can also remove all the silencers if you&#39;re trying to debug a</span>
</span><span class='line'><span class="c1"># problem that might stem from framework code.</span>
</span><span class='line'><span class="no">Rails</span><span class="o">.</span><span class="n">backtrace_cleaner</span><span class="o">.</span><span class="n">remove_silencers!</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h4 id="1.2.2.2"> 1.2.2.2 过滤参数日志</h4></p>

<hr />

<p>当有请求到你的rails应用，默认的，rails的logs文件有一些细节：请求路径,http 方法，Ip地址和参数。倘若黑客利用某些方法得到你的日志文件，那么他就能看到这些敏感信息，包括密码信息。</p>

<p>filter_parameter_logging.rb 初始化器可以让你设置哪些请求参数需要从你的log文件中过滤掉。
如果rails 接收到请求参数被你设置的filter_parameters收集了，将会在你的log文件中标记为[FILTERED]。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Configure sensitive parameters which will be filtered from the log file.</span>
</span><span class='line'><span class="no">Rails</span><span class="o">.</span><span class="n">application</span><span class="o">.</span><span class="n">config</span><span class="o">.</span><span class="n">filter_parameters</span> <span class="o">+=</span> <span class="o">[</span><span class="ss">:password</span><span class="o">]</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h4 id="1.2.2.3"> 1.2.2.3 Inflections<h4></p>

<hr />

<p>Rails 有一个Infector类，它负责将字符串变为单复数，类名变表名，模块化类名，类名变外键名等（其中一些操作有滑稽的名字，如：dasherize）
默认的，对于一些不可数的名词，ActiveSupport这个gem的infections.rb文件中。
大多数时候，Infector类有一份得体的工作，就是把类名转化为相应复数的表名。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="nv">$ </span>rails console
</span><span class='line'>&gt;&gt; ActiveSupport::Inflector.pluralize <span class="s2">&quot;project&quot;</span>
</span><span class='line'><span class="o">=</span>&gt; <span class="s2">&quot;projects&quot;</span>
</span><span class='line'>&gt;&gt; ActiveSupport::Inflector.pluralize <span class="s2">&quot;virus&quot;</span>
</span><span class='line'><span class="o">=</span>&gt; <span class="s2">&quot;viri&quot;</span>
</span><span class='line'>&gt;&gt; <span class="s2">&quot;pensum&quot;</span>.pluralize <span class="c"># Inflector features are mixed into String by default</span>
</span><span class='line'><span class="o">=</span>&gt; <span class="s2">&quot;pensums&quot;</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>然而，你可以为infector添加新规则：在config/initializers/inflections.rb 文件：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="ss">ActiveSupport</span><span class="p">:</span><span class="ss">:Inflector</span><span class="o">.</span><span class="n">inflections</span><span class="p">(</span><span class="ss">:en</span><span class="p">)</span> <span class="k">do</span> <span class="o">|</span><span class="n">inflect</span><span class="o">|</span>
</span><span class='line'>  <span class="n">inflect</span><span class="o">.</span><span class="n">plural</span> <span class="sr">/^(ox)$/i</span><span class="p">,</span> <span class="s1">&#39;\1en&#39;</span>
</span><span class='line'>  <span class="n">inflect</span><span class="o">.</span><span class="n">singular</span> <span class="sr">/^(ox)en/i</span><span class="p">,</span> <span class="s1">&#39;\1&#39;</span>
</span><span class='line'>  <span class="n">inflect</span><span class="o">.</span><span class="n">irregular</span> <span class="s1">&#39;person&#39;</span><span class="p">,</span> <span class="s1">&#39;people&#39;</span>
</span><span class='line'>  <span class="n">inflect</span><span class="o">.</span><span class="n">uncountable</span> <span class="sx">%w( fish sheep  )</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">activesupport</span><span class="o">/</span><span class="nb">test</span><span class="o">/</span><span class="n">inflector_test_cases</span><span class="o">.</span><span class="n">rb</span><span class="err">文件有一长串用</span><span class="no">Infector</span><span class="err">正确处理的复数转化列表，例如：</span>
</span><span class='line'>    <span class="s2">&quot;datum&quot;</span> <span class="o">=&gt;</span> <span class="s2">&quot;data&quot;</span><span class="p">,</span>
</span><span class='line'>    <span class="s2">&quot;medium&quot;</span> <span class="o">=&gt;</span> <span class="s2">&quot;media&quot;</span><span class="p">,</span>
</span><span class='line'>    <span class="s2">&quot;analysis&quot;</span> <span class="o">=&gt;</span> <span class="s2">&quot;analyses&quot;</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h4 id="1.2.2.4"> 1.2.2.4 自定义MIME Types</h4></p>

<hr />

<p>Rails支持标准的MIME TYPES设置(*/*, text/html, text/plain, text/javascript, text/css, text/calendar, text/csv, application/xml, application/rss+xml, application/atom+xml, application/x-yaml, multipart/form-data, application/x-www-form-urlencoded, application/json)：</p>

<p><table><tbody>
<tr><td><em>Short name</em></td> <td>respond_to<em> symbol</em></td>  <td><em>Aliases and Explanations</em> </td></tr>
<tr><td>text/html</td>  <td>:html, :xhtml </td>      <td>application/xhtml+xml</td></tr>
<tr><td>text/plain</td> <td>:text, :txt  </td>   <td>                 </td></tr>
<tr><td>text/javascript</td> <td>:js      </td> <td> application/javascript, application/x-javascript </td></tr>
<tr><td>text/css</td> <td>:css</td>   <td> Cascading style sheets     </td></tr>
<tr><td>text/calendar</td> <td>:ics</td>  <td>iCalendar format for sharing meeting requests and tasks </td></tr>
<tr><td>text/csv</td>  <td>:csv</td> <td> Comma-separated values </td></tr>
<tr><td>application/xml</td> <td>:xml</td> <td>   text/xml, application/x-xml </td></tr>
<tr><td>application/rss+xml</td> <td>:rss</td> <td>Really Simple Syndication format for web feeds</td></tr>
<tr><td>application/atom+xml</td> <td>:atom</td> <td>Atom Syndication Format for web feeds</td></tr>
<tr><td>application/x-yaml</td> <td>:yaml</td> <td>text/yaml &ndash; The human-readable data serialization format</td></tr>
<tr><td>application/x-www-form- urlencoded</td> <td>url_encoded_form</td> <td>The default content type of HTML forms</td></tr>
<tr><td>multipart/form-data</td> <td>:multipart_form</td> <td>Used for HTML forms that contain files, non-ASCII data, and
binary data</td></tr>
<tr><td>application/json</td> <td>:json</td> <td>text/x-json, application/jsonrequest-JavaScript Object Notation</td></tr>
</tbody></table></p>

<p>如果项目需要响应其他MIME TYPE，你需要再mime_types.rb文件中进行登记：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Add new mime types for use in respond_to blocks:</span>
</span><span class='line'><span class="c1"># Mime::Type.register &quot;text/richtext&quot; ,:rtf</span>
</span><span class='line'><span class="c1"># Mime::Type.register_alias &quot;text/html&quot;, :iphone</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h4 id="1.2.2.5">1.2.2.5 Secret Token</h4></p>

<hr />

<p>有些的黑客可以在服务器不知情的情况下修改该cookies内容，通过数字签名发送给浏览器cookies,而Rails能探测他们是否被捣鼓。
这和secret_token.rb文件有关，这个initializer有secret key，伴随着你的应用随机产生，用来标记cookie。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Your secret key for verifying the integrity of signed cookies.</span>
</span><span class='line'><span class="c1"># If you change this key, all old signed cookies will become invalid!</span>
</span><span class='line'>
</span><span class='line'><span class="c1"># Make sure the secret is at least 30 characters and all random,</span>
</span><span class='line'><span class="c1"># no regular words or you&#39;ll be exposed to dictionary attacks.</span>
</span><span class='line'><span class="c1"># You can use <code>rake secret</code> to generate a secure secret key.</span>
</span><span class='line'>
</span><span class='line'><span class="c1"># Make sure your secret_key_base is kept private</span>
</span><span class='line'><span class="c1"># if you&#39;re sharing your code publicly.</span>
</span><span class='line'><span class="ss">Example</span><span class="p">:</span><span class="ss">:Application</span><span class="o">.</span><span class="n">config</span><span class="o">.</span><span class="n">secret_key_base</span> <span class="o">=</span> <span class="s1">&#39;f32b1a3755e05a3d&hellip;&#39;</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>rake secret 可以重新生成secret key。</p>

<p><h4 id="1.2.2.6">1.2.2.6 Session Store</h4></p>

<hr />

<p>Rails4 session cookies加密使用的是最新cookis加密存储策略，session_store.rb这个initializer通过设置session store的type和key来配置你的应用的session存储。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="ss">Example</span><span class="p">:</span><span class="ss">:Application</span><span class="o">.</span><span class="n">config</span><span class="o">.</span><span class="n">session_store</span> <span class="ss">:encrypted_cookie_store</span><span class="p">,</span> <span class="ss">key</span><span class="p">:</span> <span class="s1">&#39;_example_session&#39;</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>session cookies 是用secret_token.rb中的secret_key_base来标记的，如果你感到困惑，可以更改secret_token.rb 的secret key值，或者运行rake secret 来重新生成secret key。</p>

<p><h4 id="1.2.2.7">1.2.2.7 参数包装<h4></p>

<hr />

<p>Rails3.1后引入的，wrap_parameters.rb这个initializer能配置你的应用与javascript mvc框架交互。（例如：backbone.js）</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Enable parameter wrapping for JSON. You can disable this by setting</span>
</span><span class='line'><span class="c1"># :format to an empt yarray.</span>
</span><span class='line'><span class="no">ActiveSupport</span><span class="o">.</span><span class="n">on_load</span><span class="p">(</span><span class="ss">:action_controller</span><span class="p">)</span> <span class="k">do</span>
</span><span class='line'>  <span class="n">wrap_parameters</span> <span class="nb">format</span><span class="p">:</span> <span class="o">[</span><span class="ss">:json</span><span class="o">]</span> <span class="k">if</span> <span class="nb">respond_to?</span><span class="p">(</span><span class="ss">:wrap_parameters</span><span class="p">)</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="c1"># To enable root element in JSON for ActiveRecord objects.</span>
</span><span class='line'><span class="c1"># ActiveSupport.on_load(:active_record) do</span>
</span><span class='line'><span class="c1">#   self.include_root_in_json = true</span>
</span><span class='line'><span class="c1"># end</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>这样到底会发生什么呢？当你向controller提交json参数时，rails将参数包裹到一个嵌套的hash中，并用controller的名字作为这个hash的key，例如：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="p">{</span><span class="s2">&quot;title&quot;</span><span class="p">:</span> <span class="s2">&quot;The Rails4 Way&quot;</span><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>将上诉代码提交到ArticlesController,将会转化成下列样子：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="p">{</span> <span class="s2">&quot;title&quot;</span><span class="p">:</span> <span class="s2">&quot;The Rails 4 Way&quot;</span><span class="p">,</span><span class="s2">&quot;article&quot;</span><span class="o">=&gt;</span><span class="p">{</span><span class="s2">&quot;title&quot;</span><span class="ss">:&quot; The Rails 4 Way&quot;</span><span class="p">}</span>  <span class="p">}</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h3 id="1.2.3">1.2.3 额外的配置</h3></p>

<hr />

<p>大多数配置选项我们可以在application.rb文件和标准的initializers文件中找到例子，这里还有一些额外的选项，你可以将它添加到额外的intializers文件中。</p>

<p><h4 id="1.2.3.1">1.2.3.1 Log-Level覆盖</h4></p>

<hr />

<p>默认的log Level是:debug，如果你有需要，也可以覆盖它；</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Force all environments to use the same logger level</span>
</span><span class='line'><span class="c1"># (by default production uses:info, the others :debug)</span>
</span><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">log_level</span> <span class="o">=</span> <span class="ss">:debug</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h4 id="1.2.3.2">1.2.3.2 Schema Dumper</h4></p>

<hr />

<p>每一次，当你运行测试代码，Rails将会用自动导出schema.rb的脚本把你的development数据库的schema导出到你的test数据库中，类似ActiveRecord的迁移脚本，事实上，他们用了相同的API。</p>

<p>如果你正在做一个与schema dumper有冲突的事，你有可能需要用SQL将它转化为旧方式schema dumper。（见注释）</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Use SQL instead of ActiveRecord&#39;s schema dumper when creating the</span>
</span><span class='line'><span class="c1"># test database. This is necessary if your schema can&#39;t be completely</span>
</span><span class='line'><span class="c1"># dumped by the schema dumper, for example, if you have constraints</span>
</span><span class='line'><span class="c1"># or db-specific column types</span>
</span><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">active_record</span><span class="o">.</span><span class="n">schema_format</span> <span class="o">=</span> <span class="ss">:sql</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h2 id="1.3">1.3 开发模式</h2></p>

<p>开发模式是rails的默认模式，也是作为开发者最长时间使用的模式，</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># File: config/environments/development.rb</span>
</span><span class='line'><span class="ss">Example</span><span class="p">:</span><span class="ss">:Application</span><span class="o">.</span><span class="n">configure</span> <span class="k">do</span>
</span><span class='line'>  <span class="c1"># Settings specified here will take precedence over those in</span>
</span><span class='line'>  <span class="c1"># config/application.rb.</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h3 id="1.3.1">1.3.1 自动加载类</h3></p>

<hr />

<p>当你在开发模式下的一个好处是快速反馈机制，当你改变代码时，只要重新刷新浏览器，就能立即看见所改的变化。</p>

<p>这个行为是由config.cache_classes设置的：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># In the development environment your application&#39;s code is reloaded on</span>
</span><span class='line'><span class="c1"># every request. This slows down response time but is perfect for</span>
</span><span class='line'><span class="c1"># development since you don&#39;t have to restart the webserver when you</span>
</span><span class='line'><span class="c1"># make code changes.</span>
</span><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">cache_classes</span> <span class="o">=</span> <span class="kp">false</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>当cache_classes为true时，Rails会运用Ruby的require去加载类，如果是false，则会用load去加载类。</p>

<ul>
<li><p>当require 一个ruby文件时，ruby解释器会执行它并且进行缓存；如果文件再次被requirmZ会忽略这次require。</p></li>
<li><p>而当你load 一个ruby文件时，不管它之前被load过几次，ruby解释器都会再次执行它。</p></li>
</ul>


<p><h4 id="1.3.1.1">1.3.1.1 The Rails Class Loader类加载器</h4></p>

<hr />

<p>在平常老版本的ruby中，不需要为了匹配脚本的内容而更改脚本的名字。在Rails中你会发现Ruby文件的名字与类或模块有联系。
Rails利用了Ruby对未知常量的回调机制，当Rails遇到未定义的常量时，它会利用类加载器(Class Loader)基于文件名的惯例去寻找并require需要的Ruby脚本。</p>

<p>那么你一定会问了，类加载器是如何找到需要的Ruby脚本的？我们已经在前面讨论了initializer.rb在Rails启动进程中的作用，Rails有一个加载路径(LOAD_PATH)的概念，默认加载路径包括你的Rails应用中任何地方的目录。</p>

<p>想要看到项目加载路径的内容，在console中输入：$LOAD_PATH</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="nv">$rails</span> console
</span><span class='line'>Loading development environment.
</span><span class='line'>&gt;&gt;<span class="nv">$LOAD_PATH</span>
</span><span class='line'><span class="o">=</span>&gt; <span class="o">[</span><span class="s2">&quot;/usr/local/lib/ruby/&hellip; # about 20 lines of output&quot;</span><span class="o">]</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>典型的Rails项目至少有60条加载路径，你可以试一试。</p>

<p><h4 id="1.3.1.2">1.3.1.2 Rails, Modules, and Auto-Loading Code</h4></p>

<hr />

<p>在Ruby中，如果你想从应用中加载其他文件的代码，你需要require声明；然而，Rails为Ruby增加一个默认行为通过建立一个简单的惯例能让Rails在大多数情况下自动加载你的代码。
如果你用过rails console，你就会发现你不用明确地require 任何代码。</p>

<p>现在我来告诉你这是如何实现的：
如果Rails遇到未定义的类或模块，它将会用以下惯例去猜测如何加载该类或模块：</p>

<p>如果该类或模块没有嵌套，则在常量名之间插入下划线：</p>

<ul>
<li><p>EstimationCalculator 将会插入：require &ldquo;estimation_calculator&rdquo;</p></li>
<li><p>KittTurboBoost 将会插入：require &ldquo;kitt_turbo_boost&rdquo;</p></li>
</ul>


<p>如果类或模块被嵌套，则会对每个模块做如上操作，并且形成对应的子目录，例如：
&ndash; MacGyver::SwissArmyKnife 变成：require &ldquo;mac_gyver/swiss_army_knife&rdquo;</p>

<ul>
<li>Example::ReallyRatherDeeply::NestedClass 变成：&#8221;example/really_rather_deeply/nested_class&#8221;，如果还没加载，Rails将会去example/really_rather_deeply/目录下寻找nested_class.rb文件，这个example/really_rather_deeply/目录会在Ruby的加载路径中查找（app/,lib/或者插件的lib/目录）</li>
</ul>


<p>所以，如果你按照rails这个规则，就基本不用怎么明确地指mZe)要加载的文件了。</p>

<p><h3 id="1.3.2">1.3.2 Eager Load</h3></p>

<hr />

<p>为了在开发模式下加快启动Rails服务的时间，你的代码一般被禁止eager loaded，你可以通过config.eager_load进行设置。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Do not eager load code on boot.</span>
</span><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">eager_load</span> <span class="o">=</span> <span class="kp">false</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>在生产模式下，你会将这个值设置为true，它会复制你的应用的大部分内容到内存中，提高web服务器的读写性能，就像Unicorn一样。</p>

<p><h3 id="1.3.3">1.3.3 错误报告</h3></p>

<p>&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;来自localhost的请求，当你想要在开发时，能够产生有用的错误信息包括debug信息（错误出现的行号等）那么设置consider_all_requests_local为true就能使rails产生这些友好的信息。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">consider_all_requests_local</span> <span class="o">=</span> <span class="kp">true</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h3 id="1.3.4">1.3.4 缓存</h3></p>

<hr />

<p>在开发模式下你一般不希望缓存行为，你真正需要它的时候是你想要去测试缓存是否正确。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">action_controller</span><span class="o">.</span><span class="n">perform_caching</span> <span class="o">=</span> <span class="kp">true</span> <span class="c1"># for testing in development model.</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>记住：当你测试完要设置为false。</p>

<p><h3 id="1.3.5">1.3.5 抛出发送错误</h3></p>

<hr />

<p>在开发模式下，rails会假定你不需要ActionMailer去抛出发送错误的异常，这个是基于config.action_mailer.raise_delivery_errors设置的。邮件发送功能不需要在开发模式下运行，特别是windows等其他平台。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Don&#39;t care if the mailer can&#39;t send.</span>
</span><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">action_mailer</span><span class="o">.</span><span class="n">raise_delivery_errors</span> <span class="o">=</span> <span class="kp">false</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>如果你真的需要在开发模式下发送邮件用来测试或排除错误，那么你可以将它设置为true。</p>

<p><h3 id="1.3.6">1.3.6 反对通知</h3></p>

<hr />

<p>当你想停止使用特定功能时，反对警告是非常有用的，config.active_support.deprecation允许你设置如何收到反对警告。在开发模式下，默认是出现在log文件中。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Print deprecation notices to the Rails logger.</span>
</span><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">active_support</span><span class="o">.</span><span class="n">deprecation</span> <span class="o">=</span> <span class="ss">:log</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h3 id="1.3.7">1.3.7 慢查询的解释</h3></p>

<hr />

<p>Rails3.2后引入的，Active Record现在监视SQL查询的门槛已经被设立。当查询花费时间超过这个设定的门槛，这个查询计划将被记录为警告。
而这个门槛的时间是由config.active_record.auto_explain_threshold_in_seconds 设置的：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Log the query plan for queries taking more than this (works)</span>
</span><span class='line'><span class="c1"># with SQLite, MySQL, and PostgreSQL).</span>
</span><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">active_record</span><span class="o">.</span><span class="n">auto_explain_threshold_in_seconds</span> <span class="o">=</span> <span class="mi">0</span><span class="o">.</span><span class="mi">5</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h3 id="1.3.8">1.3.8 待迁移错误页面</h3></p>

<hr />

<p>在Rails前面版本中，如果待迁移任务需要执行，web服务将会启动失败。
在Rails4中将会以一个错误页面展示，指示开发者运行rake db:migrate RAILS_ENV=development去解决这个问题。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Raise an error on page load if there are pending migrations</span>
</span><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">active_record</span><span class="o">.</span><span class="n">migration_error</span> <span class="o">=</span> <span class="ss">:page_load</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h3 id="1.3.9">1.3.9 Assets的Debug模式</h3></p>

<hr />

<p>Rails3.1引入Assets Pipeline，一个可以连接和缩小javascript和css的assets。
默认的，在开发模式下，javascript和css还是放在各自不同的目录中。
设置config.assets.debug 为false，将会导致Sprockets对所有assets进行连接和运行预处理器。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># Debug mode disables concatenation and preprocessing of assets.</span>
</span><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">assets</span><span class="o">.</span><span class="n">debug</span> <span class="o">=</span> <span class="kp">true</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h2 id="1.4">1.4 测试模式</h2></p>

<p>无论你在测试环境下运行rails， RAILS_ENV的值为test，然后下面的设置将会起作用。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
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</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># File: config/environments/test.rb</span>
</span><span class='line'><span class="ss">Example</span><span class="p">:</span><span class="ss">:Application</span><span class="o">.</span><span class="n">configure</span> <span class="k">do</span>
</span><span class='line'>  <span class="c1"># Settings specified here will take precedence over those in</span>
</span><span class='line'>  <span class="c1"># config/application.rb.</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># The test environment is used exclusively to run your application&#39;s</span>
</span><span class='line'>  <span class="c1"># test suite. You never need to work with it otherwise. Remember that</span>
</span><span class='line'>  <span class="c1"># your test database is &quot;scratch space&quot; for the test suite and is wiped</span>
</span><span class='line'>  <span class="c1"># and recreated between test runs. Don&#39;t rely on the data there!</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">cache_classes</span> <span class="o">=</span> <span class="kp">true</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Do not eager load code on boot. This avoids loading your whole</span>
</span><span class='line'>  <span class="c1"># application just for the purpose of running a single test. If you are</span>
</span><span class='line'>  <span class="c1"># using a tool that preloads Rails for running tests, you may have to</span>
</span><span class='line'>  <span class="c1"># set it to true.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">eager_load</span> <span class="o">=</span> <span class="kp">false</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Configure static asset server for tests with Cache-Control for</span>
</span><span class='line'>  <span class="c1"># performance.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">serve_static_assets</span> <span class="o">=</span> <span class="kp">true</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">static_cache_control</span> <span class="o">=</span> <span class="s2">&quot;public, max-age=3600&quot;</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Show full error reports and disable caching.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">consider_all_requests_local</span> <span class="o">=</span> <span class="kp">true</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">action_controller</span><span class="o">.</span><span class="n">perform_caching</span> <span class="o">=</span> <span class="kp">false</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Raise exceptions instead of rendering exception templates.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">action_dispatch</span><span class="o">.</span><span class="n">show_exceptions</span> <span class="o">=</span> <span class="kp">false</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Disable request forgery protection in test environment.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">action_controller</span><span class="o">.</span><span class="n">allow_forgery_protection</span> <span class="o">=</span> <span class="kp">false</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Tell Action Mailer not to deliver emails to the real world.</span>
</span><span class='line'>  <span class="c1"># The :test delivery method accumulates sent emails in the</span>
</span><span class='line'>  <span class="c1"># ActionMailer::Base.deliveries array.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">action_mailer</span><span class="o">.</span><span class="n">delivery_method</span> <span class="o">=</span> <span class="ss">:test</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Print deprecation notices to the stderr.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">active_support</span><span class="o">.</span><span class="n">deprecation</span> <span class="o">=</span> <span class="ss">:stderr</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure></p>

<h3>i: 自定义环境</h3>

<p><em>如果有需要，你可以给你的rails应用自定一个额外的环境，通过复制一个已经存在的环境文件(在config/environments目录中)。
自定义环境的一个共同的用法是建立一个额外的生产模式配置（例如：staging和QA development模式）。
在开发平台，你拥有进入正式环境数据库的权利吗？哈哈，使用 triage 环境就在合理不过了。运用开发模式作为正常的环境，但是数据库连接生产服务器的数据库。当你想要快速诊断生产环境下的问题，这非常有用。</em></p>

<p><h2 id="1.5">生产模式</h2></p>

<p>最后，当你部署自己的项目并接受公共请求时，生产模式是你的rails应用运行的环境。
生产模式与其他模式有一些显著的区别，不仅仅是速度的提升。</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
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</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1"># File:config/environments/production.rb</span>
</span><span class='line'>  <span class="c1"># Settings specified here will take precedence over those in</span>
</span><span class='line'>  <span class="c1"># config/application.rb.</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Code is not reloaded between requests.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">cache_classes</span> <span class="o">=</span> <span class="kp">true</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Eager load code on boot. This eager loads most of Rails and</span>
</span><span class='line'>  <span class="c1"># your application in memory, allowing both thread web servers</span>
</span><span class='line'>  <span class="c1"># and those relying on copy on write to perform better.</span>
</span><span class='line'>  <span class="c1"># Rake tasks automatically ignore this option for performance.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">eager_load</span> <span class="o">=</span> <span class="kp">true</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Full error reports are disabled and caching is turned on.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">consider_all_requests_local</span> <span class="o">=</span> <span class="kp">false</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">action_controller</span><span class="o">.</span><span class="n">perform_caching</span> <span class="o">=</span> <span class="kp">true</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Enable Rack::Cache to put a simple HTTP cache in front of your</span>
</span><span class='line'>  <span class="c1"># application</span>
</span><span class='line'>  <span class="c1"># Add <code>rack-cache</code> to your Gemfile before enabling this.</span>
</span><span class='line'>  <span class="c1"># For large-scale production use, consider using a caching reverse proxy</span>
</span><span class='line'>  <span class="c1"># like nginx, varnish or squid.</span>
</span><span class='line'>  <span class="c1"># config.action_dispatch.rack_cache = true</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Disable Rails&#39;s static asset server (Apache or nginx will</span>
</span><span class='line'>  <span class="c1"># already do this).</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">serve_static_assets</span> <span class="o">=</span> <span class="kp">false</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Compress JavaScripts and CSS.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">assets</span><span class="o">.</span><span class="n">js_compressor</span> <span class="o">=</span> <span class="ss">:uglifier</span>
</span><span class='line'>  <span class="c1"># config.assets.css_compressor = :sass</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Whether to fallback to assets pipeline if a precompiled</span>
</span><span class='line'>  <span class="c1"># asset is missed.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">assets</span><span class="o">.</span><span class="n">compile</span> <span class="o">=</span> <span class="kp">false</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Generate digests for assets URLs.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">assets</span><span class="o">.</span><span class="n">digest</span> <span class="o">=</span> <span class="kp">true</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Version of your assets, change this if you want to expire</span>
</span><span class='line'>  <span class="c1"># all your assets.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">assets</span><span class="o">.</span><span class="n">version</span> <span class="o">=</span> <span class="s1">&#39;1.0&#39;</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Specifies the header that your server uses for sending files.</span>
</span><span class='line'>  <span class="c1"># config.action_dispatch.x_sendfile_header = &quot;X-Sendfile&quot; # for Apache</span>
</span><span class='line'>  <span class="c1"># config.action_dispatch.x_sendfile_header = &#39;X-Accel-Redirect&#39;</span>
</span><span class='line'>  <span class="c1"># for nginx</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Force all access to the app over SSL, use Strict-Transport-Security,</span>
</span><span class='line'>  <span class="c1"># and use secure cookies.</span>
</span><span class='line'>  <span class="c1"># config.force_ssl = true</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Set to :debug to see everything in the log.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">log_level</span> <span class="o">=</span> <span class="ss">:info</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Prepend all log lines with the following tags.</span>
</span><span class='line'>  <span class="c1"># config.log_tags = [ :subdomain, :uuid  ]</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Use a different logger for distributed setups.</span>
</span><span class='line'>  <span class="c1"># config.logger = ActiveSupport::TaggedLogging.new(SyslogLogger.new)</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Use a different cache store in production</span>
</span><span class='line'>  <span class="c1"># config.cache_store = :mem_cache_store</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Enable serving of images, stylesheets, and JavaScripts from an</span>
</span><span class='line'>  <span class="c1"># asset server.</span>
</span><span class='line'>  <span class="c1"># config.action_controller.asset_host = &quot;<a href="http://assets.example.com&amp;quot;">http://assets.example.com&amp;quot;</a></span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Precompile additional assets.</span>
</span><span class='line'>  <span class="c1"># application.js, application.css, and all non-JS/CSS in app/assets</span>
</span><span class='line'>  <span class="c1"># folder are already added.</span>
</span><span class='line'>  <span class="c1"># config.assets.precompile += %w( search.js  )</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Ignore bad email addresses and do not raise email delivery errors.</span>
</span><span class='line'>  <span class="c1"># Set this to true and configure the email server for immediate delivery</span>
</span><span class='line'>  <span class="c1"># to raise delivery errors.</span>
</span><span class='line'>  <span class="c1"># config.action_mailer.raise_delivery_errors = false</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Enable locale fallbacks for I18n (makes lookups for any locale fall</span>
</span><span class='line'>  <span class="c1"># back to the I18n.default_locale when a translation can not be found).</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">i18n</span><span class="o">.</span><span class="n">fallbacks</span> <span class="o">=</span> <span class="kp">true</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Send deprecation notices to registered listeners.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">active_support</span><span class="o">.</span><span class="n">deprecation</span> <span class="o">=</span> <span class="ss">:notify</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Log the query plan for queries taking more than this (works</span>
</span><span class='line'>  <span class="c1"># with SQLite, MySQL, and PostgreSQL).</span>
</span><span class='line'>  <span class="c1"># config.active_record.auto_explain_threshold_in_seconds = 0.5</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Disable automatic flushing of the log to improve performance.</span>
</span><span class='line'>  <span class="c1"># config.autoflush_log = false</span>
</span><span class='line'>
</span><span class='line'>  <span class="c1"># Use default logging formatter so that PID and timestamp</span>
</span><span class='line'>  <span class="c1"># are not suppressed.</span>
</span><span class='line'>  <span class="n">config</span><span class="o">.</span><span class="n">log_formatter</span> <span class="o">=</span> <span class="o">::</span><span class="ss">Logger</span><span class="p">:</span><span class="ss">:Formatter</span><span class="o">.</span><span class="n">new</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure></p>

<p><h3 id="1.5.1">1.5.1 Assets</h3></p>

<hr />

<p>在生产模式下，assets是默认由assets pipeline预处理的。所有的文件包括application.js和application.css的assets清单被压缩和连接到他们各自的同名文件中，位于public/assets目录中。</p>

<p>如果被请求的assets不存在public/assets目录中，rails将会抛出异常。
设置config.assets.compile为true，可以在生产模式下启用live assets做后备。</p>

<p>在assets pipeline预处理时，application.css和application.js是被唯一加载的stylesheets/javascript清单文件。
想要加载其他assets，在定义config.assets.precompile的地方设置就行了：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">assets</span><span class="o">.</span><span class="n">precompile</span> <span class="o">+=</span> <span class="sx">%w( administration.css  )</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>像Rails大多数特征一样，Asset Pipeline 的用法完全是可选的，config.assets.enabled设置为false</p>

<p><h3 id="1.5.2">1.5.2 Asset 主机</h3></p>

<hr />

<p>默认地，Rails通过当前主机的public/ 目录连接assets，但是你可以直接将assets连接到一个assets服务器。config.action_controller.asset_host在后面章节会讲到。</p>

<p><h2 id="1.6">1.6 日志</h2></p>

<p>Rails的大多数编程环境<em>（models, controllers, view templates）有logger属性</em>，遵从Log4r接口或默认Ruby1.8+Logger类。</p>

<p>无法在你的代码中获得日志的引用？利用Rails.logger 方法你可以在任何地方引用日志。
我们非常容易创建一个新的日志，见下面例子：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="nv">$ </span>irb
</span><span class='line'>&gt; require <span class="s1">&#39;logger&#39;</span>
</span><span class='line'><span class="o">=</span>&gt; <span class="nb">true</span>
</span><span class='line'>
</span><span class='line'>irb<span class="o">(</span>main<span class="o">)</span>:002:0&gt; <span class="nv">logger</span> <span class="o">=</span> Logger.new <span class="nv">STDOUT</span>
</span><span class='line'><span class="o">=</span>&gt;#&lt;Logger:0x32db4c@level<span class="o">=</span>0,@progname<span class="o">=</span>nil,@logdev<span class="o">=</span>
</span><span class='line'><span class="c">#&lt;Logger::LogDevice:0x32d9bc&hellip;&gt;</span>
</span><span class='line'>
</span><span class='line'>&gt; logger.warn <span class="s2">&quot;do not want!!!&quot;</span>
</span><span class='line'>W, <span class="o">[</span>2013-02-01T10:59:26.896825 <span class="c">#6243] WARN &mdash; : do not want!!!</span>
</span><span class='line'><span class="o">=</span>&gt; <span class="nb">true</span>
</span><span class='line'>
</span><span class='line'>&gt; logger.info <span class="s2">&quot;in your logger, giving info&quot;</span>
</span><span class='line'>I, <span class="o">[</span>2013-02-01T10:59:42.478325 <span class="c">#6243] INFO &mdash; : in your logger, giving info</span>
</span><span class='line'><span class="o">=</span>&gt; <span class="nb">true</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>你可以利用logger将信息加入日志无论它什么时候产生，这些日志信息运用对应程度的方法。
标准的日志程度有：</p>

<ul>
<li><p><strong>debug</strong> : 运用debug捕获数据和有用的应用状态来排除错误。这种级别通常不会被捕获到production日志中。</p></li>
<li><p><strong>info</strong> : 运用info捕获信息报文。我喜欢运用这种日志级别在良好应用程序情况下记录非正常事件的时间戳。</p></li>
<li><p><strong>warn</strong> : 用warn级别捕获那些不平常的可能值得调查的事件。有时候，我会抛出warning日志去阻止用户做一些我不允许做的事情。
我的目的是对那些坏恶意的用户或是漏洞继续保持我的应用的界面友好性。如下例子：</p></li>
</ul>


<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">def</span> <span class="nf">create</span>
</span><span class='line'>  <span class="k">begin</span>
</span><span class='line'>    <span class="n">group</span><span class="o">.</span><span class="n">add_member</span><span class="p">(</span><span class="n">current_user</span><span class="p">)</span>
</span><span class='line'>    <span class="n">flash</span><span class="o">[</span><span class="ss">:notice</span><span class="o">]</span> <span class="o">=</span> <span class="s2">&quot;Successfully joined </span><span class="si">#{</span><span class="n">scene</span><span class="o">.</span><span class="n">display_name</span><span class="si">}</span><span class="s2">&quot;</span>
</span><span class='line'>  <span class="k">rescue</span> <span class="ss">ActiveRecord</span><span class="p">:</span><span class="ss">:RecordInvalid</span>
</span><span class='line'>    <span class="n">flash</span><span class="o">[</span><span class="ss">:error</span><span class="o">]</span> <span class="o">=</span> <span class="s2">&quot;You are already a member of </span><span class="si">#{</span><span class="n">group</span><span class="o">.</span><span class="n">name</span><span class="si">}</span><span class="s2">&quot;</span>
</span><span class='line'>    <span class="n">logger</span><span class="o">.</span><span class="n">warn</span> <span class="s2">&quot;A user tried to join a group twice. UI should</span>
</span><span class='line'><span class="s2">    not have allowed it.&quot;</span>
</span><span class='line'>  <span class="k">end</span>
</span><span class='line'>  <span class="n">redirect_to</span> <span class="ss">:back</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure></p>

<ul>
<li><p><strong>error</strong> : 运用error级别捕获那些不需要重新启动服务的错误信息。</p></li>
<li><p><strong>fatal</strong> : 可以想象最坏情况的发生：你的应用挂了，并且需要手动重启。</p></li>
</ul>


<p><h3 id="1.6.1">1.6.1 Rails的日志文件</h3></p>

<hr />

<p>Rails的log目录中有三个对应三种标准环境的log文件，随着时间的增长，这些文件会不断变大。这里介绍一个rake任务，可以简单地清理这些log文件：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="nv">$ </span>rake log:clear <span class="c"># Truncates all *.log files in log/ to zero bytes</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>当你在工作时，log/development.log显得非常有用，许多程序员会在他们编程时打开另一个终端并持续显示开发模式下的日志尾部信息：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="nv">$ </span>tail -f log/development.log
</span><span class='line'>
</span><span class='line'>Article Load <span class="o">(</span>0.2ms<span class="o">)</span>  SELECT <span class="s2">&quot;articles&quot;</span>.* FROM <span class="s2">&quot;articles&quot;</span> WHERE
</span><span class='line'>  <span class="s2">&quot;articles&quot;</span>.<span class="s2">&quot;id&quot;</span> <span class="o">=</span> <span class="nv">$1</span> LIMIT 1  <span class="o">[[</span><span class="s2">&quot;id&quot;</span>, <span class="s2">&quot;1&quot;</span><span class="o">]]</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>在development的日志中各种有价值的信息是非常有用的。举个例子，每次你发一个请求，一串有用的信息将会出现在你的日志中，这是我项目的样本：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>Started GET<span class="s2">&quot;/user_photos/1&quot;</span> <span class="k">for </span>127.0.0.1 at 2007-06-0617:43:13
</span><span class='line'>  Processing by UserPhotosController#show as HTML
</span><span class='line'>  Parameters: <span class="o">{</span><span class="s2">&quot;/users/8-Obie-Fernandez/photos/406&quot;</span><span class="o">=</span>&gt;nil,
</span><span class='line'>  <span class="s2">&quot;action&quot;</span><span class="o">=</span>&gt;<span class="s2">&quot;show&quot;</span>, <span class="s2">&quot;id&quot;</span><span class="o">=</span>&gt;<span class="s2">&quot;406&quot;</span>, <span class="s2">&quot;controller&quot;</span><span class="o">=</span>&gt;<span class="s2">&quot;user_photos&quot;</span>,
</span><span class='line'>  <span class="s2">&quot;user_id&quot;</span><span class="o">=</span>&gt;<span class="s2">&quot;8-Obie-Fernandez&quot;</span><span class="o">}</span>
</span><span class='line'>  User Load <span class="o">(</span>0.4ms<span class="o">)</span>  SELECT * FROM users WHERE <span class="o">(</span>users.<span class="s1">&#39;id&#39;</span> <span class="o">=</span> 8<span class="o">)</span>
</span><span class='line'>  Photo Load <span class="o">(</span>0.9ms<span class="o">)</span>  SELECT * FROM photos WHERE <span class="o">(</span>photos.<span class="s1">&#39;id&#39;</span> <span class="o">=</span> 406
</span><span class='line'>  AND <span class="o">(</span>photos.resource_id <span class="o">=</span> 8 AND photos.resource_type <span class="o">=</span> <span class="s1">&#39;User&#39;</span><span class="o">))</span>
</span><span class='line'>  CACHE <span class="o">(</span>0.0ms<span class="o">)</span>   SELECT * FROM users WHERE <span class="o">(</span>users.<span class="s1">&#39;id&#39;</span> <span class="o">=</span> 8<span class="o">)</span>
</span><span class='line'>Rendered adsense/<em>medium_rectangle<span class="o">(</span>1.5ms<span class="o">)</span>
</span><span class='line'>  User Load <span class="o">(</span>0.5ms<span class="o">)</span> SELECT * FROM users WHERE <span class="o">(</span>users.<span class="s1">&#39;id&#39;</span> <span class="o">=</span> 8<span class="o">)</span>
</span><span class='line'>  LIMIT 1
</span><span class='line'>  SQL <span class="o">(</span>0.4ms<span class="o">)</span> SELECT count<span class="o">(</span>*<span class="o">)</span> AS count_all FROM messages WHERE
</span><span class='line'>  <span class="o">(</span>messages.receiver_id <span class="o">=</span> 8 AND <span class="o">(</span>messages.<span class="s1">&#39;read&#39;</span> <span class="o">=</span> 0<span class="o">))</span>
</span><span class='line'>Rendered layouts/</em>header<span class="o">(</span>25.3ms<span class="o">)</span>
</span><span class='line'>Rendered adsense/<em>leaderboard<span class="o">(</span>0.4ms<span class="o">)</span>
</span><span class='line'>Rendered layouts/</em>footer<span class="o">(</span>0.8ms<span class="o">)</span>
</span><span class='line'>Rendered photos/show.html.erb within layouts/application.html.erb<span class="o">(</span>38.9ms<span class="o">)</span>
</span><span class='line'>Completed in 99ms<span class="o">(</span>Views:37.4ms|ActiveRecord:12.3ms<span class="o">)</span> with 200
</span></code></pre></td></tr></table></div></figure></p>

<p>下列列出日志中所有数据项包括的内容：</p>

<ul>
<li><p>controller和action的调用</p></li>
<li><p>发出请求的的远程计算机IP地址</p></li>
<li><p>请求发生的时间戳</p></li>
<li><p>请求的<em>session ID</em></p></li>
<li><p>请求的参数hash</p></li>
<li><p>请求的数据库信息，包括话费的时间和数据库执行语句</p></li>
<li><p>缓存查询的命中信息：包括话费的时间和SQL语句从缓存中触发结果而不是往返数据库。</p></li>
<li><p>渲染每个模板视图的输出及其话费的时间</p></li>
<li><p>完成一个请求的合计时间</p></li>
<li><p>数据库操作和渲染的时间分析</p></li>
<li><p>HTTP的状态码和响应客户端的URL</p></li>
</ul>


<p><h3 id="1.6.2">1.6.2 标记日志</h3></p>

<hr />

<p>日志信息有大范围数量信息，想要跟踪问题或特殊请求显得非常困难。为了减轻这种情况，Rails3.2引入了一种可以标记日志信息的能力。
最简单的方法去添加标记到你的日志文件，就是去包含一个响应请求对象的方法，设置config.log_tags。
举例，设置config.log_tags 去包含:subdomain：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">config</span><span class="o">.</span><span class="n">log_tags</span> <span class="o">=</span> <span class="o">[</span><span class="ss">:subdomain</span><span class="o">]</span>
</span></code></pre></td></tr></table></div></figure></p>

<p>这将导致对每个日志信息请求前面都加上一个子域：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="o">[</span>admin<span class="o">]</span>Started GET <span class="s2">&quot;/articles&quot;</span> <span class="k">for </span>127.0.0.1 at 2013-02-01 11:49:09-0500
</span></code></pre></td></tr></table></div></figure></p>

<p><h3 id="1.6.3">1.6.3 日志文件分析</h3></p>

<hr />

<p>一些非正式的分析，可以使用development日志的输出和一些常识判断。
<strong>性能：</strong> 更明显的分析之一是研究你的应用的性能。你的请求越快，你的rails进程就能处理越多的请求。这就是为什么性能数据通常用每秒来表示请求，这样你就可以通过查找渲染和查询语句来分析为什么花费那么长时间。</p>

<p>要意识到日志文件记录的报告并不是非常准确，这点很重要。事实上，如果单单从内部本身很难衡量事物的时间，错误可能更多。
为任何给定的请求加上渲染和数据库时间百分比，不会总是接近100%的。</p>

<p>但是，尽管在纯粹客观的意义上不准确，在同一个应用中对数据报告时间进行主观判断也是完美的。它给你一个途径去判断这个action是不是比之前花费更长的时间；或者是不是比其他的action速度更快或更慢，等等。</p>

<p><strong>SQL查询：</strong>
Active Record 没有像预期的那样执行？事实上，记录在日志文件的Active Record可以帮助你排除一些由复杂的查询导致的问题。</p>

<p><strong>鉴别N+1选择问题：</strong>
无论什么时候，当你在展示一条关联其他记录的记录时，你可能会面对一种叫做N+1的选择问题。你将会意识到这些<em>选择语句只有主键的值是不同的</em>。</p>

<p>举个例子，下面是一个真实的项目中日志文件片段，当FlickrPhoto 实例被加载时产生的N+1问题：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>FlickrPhoto Load <span class="o">(</span>1.3ms<span class="o">)</span> SELECT * FROM flickr_photos WHERE
</span><span class='line'><span class="o">(</span>flickr_photos.resource_id <span class="o">=</span> 15749 AND flickr_photos.resource_type <span class="o">=</span>
</span><span class='line'> <span class="s1">&#39;Place&#39;</span> AND <span class="o">(</span>flickr_photos.<span class="s1">&#39;profile&#39;</span> <span class="o">=</span> 1<span class="o">))</span> ORDER BY updated_at desc
</span><span class='line'>LIMIT 1
</span><span class='line'>
</span><span class='line'>FlickrPhoto Load <span class="o">(</span>1.7ms<span class="o">)</span> SELECT * FROM flickr_photos WHERE
</span><span class='line'><span class="o">(</span>flickr_photos.resource_id <span class="o">=</span> 15785 AND flickr_photos.resource_type <span class="o">=</span>
</span><span class='line'><span class="s1">&#39;Place&#39;</span> AND <span class="o">(</span>flickr_photos.<span class="s1">&#39;profile&#39;</span> <span class="o">=</span> 1<span class="o">))</span> ORDER BY updated_at desc
</span><span class='line'>LIMIT 1
</span><span class='line'>
</span><span class='line'>FlickrPhoto Load <span class="o">(</span>1.4ms<span class="o">)</span> SELECT * FROM flickr_photos WHERE
</span><span class='line'><span class="o">(</span>flickr_photos.resource_id <span class="o">=</span> 15831 AND flickr_photos.resource_type <span class="o">=</span>
</span><span class='line'><span class="s1">&#39;Place&#39;</span> AND <span class="o">(</span>flickr_photos.<span class="s1">&#39;profile&#39;</span> <span class="o">=</span> 1<span class="o">))</span> ORDER BY updated_at desc
</span><span class='line'>LIMIT 1
</span></code></pre></td></tr></table></div></figure></p>

<p>等等，是不是觉得很熟悉？
幸运的是，这些语句执行速度还是非常快的，每条接近0.0015 秒。缺少减轻的因素，我将面临一连串待处理的性能问题。当你的数据库在一个单独的机器上，这个问题将非常严重，他将处理每一条查询而造成网络延迟。</p>

<p>N+1问题并不可怕，很多时候只需要在特定的查询语句使用includes方法就能解决问题。</p>

<h3>i: 关注分离（Separation of Concerns）</h3>

<p> <em>一个精心设计的MVC应用遵循一定的协议：逻辑层数据库操作必然在model中执行，视图完成渲染任务。一般而言，你的controller需要渲染视图，必须通过model到数据库获取数据。在Rails中，controller完成对model查询的数据的处理并进行视图的渲染。</em></p>

<p>在渲染过程中进行数据库的访问是一种非常不好的做法。直接从模板的代码中调用数据库方法背离了<strong>关注分离</strong>原则，简直是一个恶梦。</p>

<p>然而有其他方法可以在你渲染模板时含蓄的访问数据库，通过model进行封装，可能用lazy loading关联触发。
我们可以不容置疑地说这是不好的做法吗？其实这很难说。有一些情况是需要在渲染时访问数据库的（如利用片段缓存的）。</p>

<h3>i: 使用备用的Logging schemes</h3>

<p>这很简单，仅仅只要指定一个和Ruby的Logger兼容的类，像ActiveRecord::Base.logger。David曾经说过一个厉害的黑客必须具备交换日志的能力。在控制台会话期间，为了在控制台看到你的SQL语句生成正确，需要指定一个新的Logger实例指向STDOUT到ActiveRecord::Base.logger。
Jamis也完整地写了关于这个的技术博文：<a href="http://weblog.jamisbuck.org/2007/1/31/more-on-watching-activerecord">http://weblog.jamisbuck.org/2007/1/31/more-on-watching-activerecord</a></p>

<p><h4 id="1.6.3.1">1.6.3.1  Rails::Subscriber.colorize_logging</h4></p>

<hr />

<p>告诉Rails是否使用ANSI代码使日志语句有颜色，颜色可以帮助我们更好地阅读日志文件（除了windows），当你使用系统日志时，也可能使问题复杂化。
默认是true，如果你发现你的软件不支持ANSI代码日志文件颜色化功能，请将它改为false。</p>

<p>以下片段是带有ANSI代码的日志片段：</p>

<p><figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'>^<span class="o">[[</span>4;36;1mSQL <span class="o">(</span>0.0ms<span class="o">)</span>^<span class="o">[[</span>0m ^<span class="o">[[</span>0;1mMysql::Error: Unknown table
</span><span class='line'><span class="s1">&#39;expense_reports&#39;</span>:DROPTABLEexpense_reports^<span class="o">[[</span>0m
</span><span class='line'>  ^<span class="o">[[</span>4;35;1mSQL <span class="o">(</span>3.2ms<span class="o">)</span>^<span class="o">[[</span>0m ^<span class="o">[[</span>0mCREATE TABLE expense_reports <span class="o">(</span><span class="s1">&#39;id&#39;</span>
</span><span class='line'>int<span class="o">(</span>11<span class="o">)</span> DEFAULT NULL auto_increment PRIMARYKEY,<span class="s1">&#39;user_id&#39;</span> int<span class="o">(</span>11<span class="o">))</span>
</span><span class='line'>                    &hellip;<span class="o">]]</span>..<span class="o">]]</span>..<span class="o">]]</span>..<span class="o">]]</span>..<span class="o">]]</span>..<span class="o">]]</span>..<span class="o">]]</span>
</span></code></pre></td></tr></table></div></figure></p>

<h4>Wilson 说：</h4>

<blockquote><p>我见过的几乎没有人知道怎样将日志颜色化，-R选项。</p></blockquote>

<h4>i: 系统日志syslog</h4>

<p>像Unix系统的系统都有一个系统服务叫做系统日志。因为各种原因，它可能是一个更好的选择。</p>

<ul>
<li><p>更细粒度控制日志级别和内容</p></li>
<li><p>多个Rails应用的日志整合输出</p></li>
<li><p>如果你使用多系统远程日志功能，多个rails应用的日志整合输出是可能的，比起单独处理每个应用程序服务器上的单独日志文件好得多。</p></li>
</ul>


<p><h3 id="1.6.4">1.6.4 总结</h3></p>

<hr />

<p>我们结束了Rails之旅，这章简要覆盖了bundler的一些细节，并且评估了不同环境下rails的执行，和如何加载它的依赖，包括你的应用代码。并且深入查看application.rb文件和如何更改每种模式来自定义符合我们胃口的Rails的行为。</p>
]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[PS 查看进程]]></title>
    <link href="https://TsaiKoga.github.com/blog/2014/04/23/ps-cha-kan-jin-cheng/"/>
    <updated>2014-04-23T13:53:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2014/04/23/ps-cha-kan-jin-cheng</id>
    <content type="html"><![CDATA[<p>如果你使用Linux进行操作，不可避免要接触ps命令，他可以显示进程。</p>

<p>首先，我们来介绍一下进程：</p>

<p>1.<strong> 进程 </strong></p>

<hr />

<p>linux上进程有5种状态:</p>

<blockquote><ol>
<li>运行(正在运行或在运行队列中等待)</li>
<li>中断(休眠中, 受阻, 在等待某个条件的形成或接受到信号)</li>
<li>不可中断(收到信号不唤醒和不可运行, 进程必须等待直到有中断发生)</li>
<li>僵死(进程已终止, 但进程描述符存在, 直到父进程调用wait4()系统调用后释放)</li>
<li>停止(进程收到SIGSTOP, SIGSTP, SIGTIN, SIGTOU信号后停止运行运行</li>
</ol>
</blockquote>

<br/>


<p>2.<strong> 常用的PS参数</strong></p>

<hr />

<p>1）ps a    显示现行终端机下的所有程序，包括其他用户的程序。</p>

<p>2）ps -A   显示所有程序。</p>

<p>3）ps c    列出程序时，显示每个程序真正的指令名称，而不包含路径，参数或常驻服务的标示。</p>

<p>4）ps -e   此参数的效果和指定&#8221;A&#8221;参数相同。</p>

<p>5）ps e    列出程序时，显示每个程序所使用的环境变量。</p>

<p>6）ps f    用ASCII字符显示树状结构，表达程序间的相互关系。</p>

<p>7）ps -H   显示树状结构，表示程序间的相互关系。</p>

<p>8）ps -N   显示所有的程序，除了执行ps指令终端机下的程序之外。</p>

<p>9）ps s    采用程序信号的格式显示程序状况。</p>

<p>10）ps S   列出程序时，包括已中断的子程序资料。</p>

<p>11）ps -t &lt;终端机编号> 　指定终端机编号，并列出属于该终端机的程序的状况。</p>

<p>12）ps u 　以用户为主的格式来显示程序状况。</p>

<p>13）ps x 　显示所有程序，不以终端机来区分。</p>

<p>14）ps -l  較長,較詳細的顯示該PID的信息</p>

<br/>


<p>3.<strong> 最常用的ps aux 命令解析 </strong></p>

<hr />

<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
</pre></td><td class='code'><pre><code class='sh'><span class='line'><span class="c"># ps aux |more</span>
</span><span class='line'>    USER       PID        %CPU %MEM   VSZ  RSS  TTY                   STAT     START   TIME     COMMAND
</span><span class='line'>    root         1        0.0  0.0     4772  564 ?                     S        Sep22   0:03     init <span class="o">[</span>3<span class="o">]</span>
</span><span class='line'>    root         2        0.0  0.0     0    0        ?                 S        Sep22   0:03     <span class="o">[</span>migration/0<span class="o">]</span>
</span><span class='line'>    root         3        0.0  0.0     0    0        ?                 SN      Sep22   0:00     <span class="o">[</span>ksoftirqd/0<span class="o">]</span>
</span><span class='line'>    root         4        0.0  0.0     0    0        ?                 S        Sep22   0:02     <span class="o">[</span>migration/1<span class="o">]</span>
</span><span class='line'>    root         5        0.0  0.0     0    0        ?                 SN      Sep22   0:00     <span class="o">[</span>ksoftirqd/1<span class="o">]</span>
</span><span class='line'>    root         6        0.0  0.0     0    0        ?                 Ss+     Sep22   0:02     <span class="o">[</span>migration/2<span class="o">]</span>
</span><span class='line'>    root         7        0.0  0.0     0    0        ?                 SN      Sep22   0:00     <span class="o">[</span>ksoftirqd/2<span class="o">]</span>
</span><span class='line'>    root         8        0.0  0.0     0    0        ?                 S        Sep22   0:00     <span class="o">[</span>migration/3<span class="o">]</span>
</span><span class='line'>    root         9        0.0  0.0     0    0        ?                 SN      Sep22   0:00     <span class="o">[</span>ksoftirqd/3<span class="o">]</span>
</span><span class='line'>    root        10        0.0  0.0     0    0        ?                 S&lt;      Sep22    0:00     <span class="o">[</span>migration/4<span class="o">]</span>
</span></code></pre></td></tr></table></div></figure>


<p>上面的每一列代表的意思：</p>

<ol>
<li>USER 进程的属主；</li>
<li>PID   进程的ID；</li>
<li>PPID    父进程；</li>
<li>%CPU   进程占用的CPU百分比；</li>
<li>%MEM  占用内存的百分比；</li>
<li>NI        进程的NICE值，数值大，表示较少占用CPU时间；</li>
<li>VSZ     該进程使用的虚拟內存量（KB）；</li>
<li>RSS     該進程占用的固定內存量（KB）（驻留中页的数量）；</li>
<li>TTY     該進程在那個終端上運行（登陸者的終端位置），若與終端無關，則顯示（？）。若為pts/0等，則表示由網絡連接主機進程</li>
<li>WCHAN  當前進程是否正在進行，若為-表示正在進行；</li>
<li>START   該進程被觸發启动时间；</li>
<li>TIME      該进程實際使用CPU運行的时间；</li>
<li>COMMAND   命令的名称和参数；</li>
</ol>


<br/>


<h4>对于Stat的常见状态：</h4>

<p>D 无法中断的休眠状态（通常 IO 的进程）；</p>

<p>R 正在运行可中在队列中可过行的；</p>

<p>S 处于休眠状态；</p>

<p>T 停止或被追踪；</p>

<p>W 进入内存交换  （从内核2.6开始无效）；</p>

<p>X 死掉的进程   （基本很少見）；</p>

<p>Z 僵尸进程；</p>

<p>&lt; 优先级高的进程</p>

<p>N 优先级较低的进程</p>

<p>L 有些页被锁进内存；</p>

<p>s 进程的领导者（在它之下有子进程）；</p>

<p>l 多进程的（使用 CLONE_THREAD, 类似 NPTL pthreads）；</p>

<ul>
<li>位于后台的进程组；</li>
</ul>

]]></content>
  </entry>
  
  <entry>
    <title type="html"><![CDATA[敏捷开发]]></title>
    <link href="https://TsaiKoga.github.com/blog/2014/02/25/min-jie-kai-fa/"/>
    <updated>2014-02-25T13:23:00+08:00</updated>
    <id>https://TsaiKoga.github.com/blog/2014/02/25/min-jie-kai-fa</id>
    <content type="html"><![CDATA[<p><img src="https://TsaiKoga.github.com/images/posts/2014-02-25/minjie.jpg" title="敏捷开发图" alt="图片无法显示" /></p>

<h5>敏捷开发的定义：</h5>

<p>是一种<strong>以人为核心、迭代、循环渐进的开发方法</strong>。在敏捷开发中项目被切分为多个子项目，各个子项目的成果都经过测试，具备集成和可运行的特征。简而言之，就是把一个大项目切分成多个<strong>相互联系但可独立运行的子项目</strong>，并<strong>分别完成</strong>。在此过程软件一直处于可使用状态。</p>

<h5>敏捷开发 5 大价值观</h5>

<ol>
<li>沟通: 团队内部的开发人员之间沟通。</li>
<li>简单: 就是指简单的建模，如画一两张图表来代替几十甚至几百行的代码。</li>
<li>反馈: 过度自信是编程的职业病，反馈则是其处方。</li>
<li>勇气: 当你的决策证明是不合适的时候，你就需要做出重大的决策，放弃或重构你的工作，修正你的方向。</li>
<li>谦逊: 这个就不用我解释了。</li>
</ol>


<h5>敏捷开发核心做法</h5>

<ol>
<li>测试驱动开发</li>
<li>结对编程: 指<strong>两位程序员</strong>肩并肩地坐在同一台电脑前<strong>合作完成</strong>同一个设计、同一个算法、同一段代码或同一组测试。</li>
<li>持续集成:</li>
<li>每日站立会议</li>
<li>共同拥有代码</li>
<li>系统隐喻</li>
</ol>


<p> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;除了敏捷开发模式，目前所具有的开发模式还有好几种,如：瀑布模型，快速原型模型，增量模型，螺旋模型，喷泉模型。
 我在大学的实验室中使用 Rails 框架进行开发，使用的是敏捷开发模式。虽然如此，但是我们团队的敏捷开发还是带有其他模型的特征，可能因为我们还是学生团队，不是一个真正意义上的商业团队(我们平常还必须上课)。</p>

<p> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;我先通过我们团队负责的一个项目（在这里我们叫它为ce）来阐述，我们为什么不是真正的敏捷，而是有有快速原型和增量的特征的敏捷，或者说我们是采用混合模式。</p>

<p><span style="text-align:center"><img src="https://TsaiKoga.github.com/images/posts/2014-02-25/zengliang.jpg" title="增量模型图" alt="图片无法显示" /></span></p>

<ol>
<li><p>ce 首先通过实现前台大部分界面（没有功能）的<strong>样品给客户观看并给予讲解</strong>。客户可以清楚的看到有具体形态而无功能的样品，从而有助于客户提出有<strong>针对性的修改意见</strong>。而参与调研的师兄们对<strong>样品进行再次修改</strong>，并再次呈现给客户看，直到双方达成共识为止；之后师兄们就对这些调研后的资料进行讨论并据此形成<strong>规格说明文档</strong>（我们的规格说明文档是前台界面的图片，并用文字等方式对其功能进行阐述，当然还有一些流程图），然后把之前做的不具有功能的<strong>样品抛弃</strong>。很明显这是<strong>结合了快速原型模型</strong>，从而得到它的<strong>优点</strong>：规格说明文档<strong>正确的描述客户的需求</strong>，减少了设计和编码阶段发生的可能性错误。</p></li>
<li><p>当进入开发阶段时，团队要求将这个 ce 项目分成三期；每期有几条流程，而各个阶段的流程互不影响。并在第一期开发结束后部署给企业使用，这样企业就能拥有<strong>充裕的时间学习和适应</strong>此系统,减少一个新系统可能给客户组织带来的冲击。第二期进行开发直至完成后再部署给企业，这样企业已经事先使用过系统，对系统的排斥性不会那么强了。<strong>增量模型是将软件产品作为一系列的增量构件来设计，编码，集成和测试</strong>。而 ce 的这种开发方式明显和增量模型类似,当然，也可以说是<strong>敏捷开发的增量交付</strong>。</p></li>
<li><p>最后，我想要通过实验室的 ce 项目来说明敏捷开发的特征。</p></li>
</ol>


<p><strong>持续集成：</strong>一开始，我已经提到 ce 调研，那时候形成的规格说明文档有项目每个页面的设计方式，这样 ce 的每个模块以及每个页面都已经划分好，剩下的就是开发人员对每个页面的实现。实现一个页面后进行白盒测试，一个模块的所有页面完成时进行集成测试，这符合敏捷开发的方式。</p>

<p><strong>测试驱动开发：</strong>很可惜，团队的成员（包括老成员）没有 <strong>TDD (测试驱动开发)</strong> 的经验，我们使用一个星期的时间学习，最后在讨论中决定不使用 TDD，主要原因是 TDD 讲究先写测试后开发，而我们已经进入了开发阶段；再加上没有经验，如果使用TDD很大可能会拖慢项目进度。</p>

<p><strong>每日站立会议：</strong>我们每天都会在实验室进行工作，并且在每天晚上进行一个名叫<strong>三分钟站立会议</strong>的谈论，这个会议是就是要求每个人用三分钟左右的时间回报当天的工作内容、任务目标及所遇到的问题；我们希望从这次会议<strong>获得团队中每个人的任务进度和状态，从而有效的对进度进行把控</strong>。这就符合敏捷开发的五大价值观的其中两个：<strong>沟通</strong>和<strong>反馈</strong>。</p>

<p>我清楚的记得我当初被任命开发一个叫做“生产通知单”的页面，这个页面设计上不合理，集结了很多表，关系复杂，数据量大，并且由于 Extjs 特性，导致页面加载速度慢。后来团队选择废除这个页面，上千行的代码就这样被废除了。这也符合敏捷开发的一大价值观：<strong>勇气</strong>。</p>

<p><strong>系统拥有共同的代码：</strong>我们使用 Git 对 ce 的代码进行版本管理，由于 Git 巧妙的设计，团队<strong>每个成员都用有 ce 的代码</strong>（可能是各自不同的版本），不会因为仓库的代码错误和丢失而导致项目失败。</p>

<p><strong>代码的评审和重构：</strong>由于进入第一期末尾时，发现有很多 bug ，最终讨论设立一个代码评审人员(一个师兄，他的经验比我们丰富)，他负责对代码进行评审，并将需要重构的代码标记出来形成一个新的任务，将任务授予相应的开发人员。</p>
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